Here there is an apparent contradiction — the sutra clearly insists that there is no time in which the Buddha is not present, but it also claims that he became a buddha. Chapter 16 answers Maitreya’s question at the end of chapter 15 by teaching that Śākyamuni has been a buddha from the very remote past, but this does not explain how he both always is and yet became enlightened. What is involved here, I think, is that on the one hand, in order both to affirm this world and to identify the Buddha with the Dharma, the everlasting process which is the truth about the nature of things, it is important to have him be eternal or everlasting. Just as there is, and can be, no place from which the Buddha is completely absent, there is no time in which the Buddha is not present. On the other hand, the very meaning of “enlightenment” requires that it be a process, and thus requires that Śākyamuni Buddha became enlightened. In fact, in several places the Lotus Sutra teaches that Śākyamuni Buddha became enlightened only after countless kalpas of bodhisattva practice. Further, only if he became enlightened could Śākyamuni Buddha be a model for others or an encouragement for them to enter the Buddha-way. So an apparent contradiction remains unresolved.

The sutra can be indifferent to such problems because they are soteriologically unimportant. Just as in chapter 24 when the Bodhisattva Wonderful Voice expresses to the Buddha of his own land his desire to visit the sahā world to pay tribute to Śākyamuni Buddha, and that Buddha warns him that even though the sahā world is not smooth or clean and its buddha and bodhisattvas are short, he should not disparage or make little of that world or think that its buddha and bodhisattvas are inferior. In this story too the point is that the sahā world is not to be regarded as inferior. In other words, the real point here is an affirmation of the sahā world. It is, we are told, a world which should not look for help from other worlds because it does not need help from elsewhere.

Thus the use of miracle stories in the Lotus Sutra is exactly the opposite of what is so often the case. Instead of using stories of other worlds as a way of encouraging escape from or negligence toward this world, in the Lotus Sutra stories of other worlds are used to radically affirm the reality and importance of this world.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 185-186

Exactly what is meant by the empty space in the lower part of the sahā world below the earth is unclear. Probably it is simply the most convenient way to have this huge number of bodhisattvas be hidden, yet not be in the less than human regions within the earth, and not be among the heavenly deities, yet still be in the sahā world. In other words, both for the sake of the story and for the sake of the central message of the Lotus Sutra, it is important that these bodhisattvas be both hidden and of this world.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 184

In the [Parable Of The Skillful Physician And His Sick Children], the physician-father of course represents the Buddha, and his supposed death is like the Buddha’s entry into nirvana. In reality, in the view of the Lotus Sutra, the universal Buddha, the loving father of the world who is working to save all from suffering, has not and will not pass away. He pretends to pass away only in order to get people to be more responsible for their own lives. This is a good example of how the sutra takes what is a basically negative notion, nirvana, and turns it into a world-affirmative one.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 183

The idea in the story of the jeweled Stupa that Śākyamuni Buddha creates a unified world out of many worlds is especially significant. The Lotus Sutra is an integrative sutra. Throughout, it emphasizes unity, oneness, integration, some kind of coming together. As the truth is ultimately one, i.e., without internal contradiction, so too the teachings of the Buddha who discovered the truth must be one. That is, finally there can be only one Buddha-way. But in the Lotus Sutra, the one does not destroy or denigrate the many. Though integrated, though the many become as one, they remain many. The cosmos only exists by virtue of the fact that it has worlds. Similarly, in the Lotus Sutra, the teaching, the Buddha Dharma, only exists by virtue of the many teachings. Neither right views nor right living can be a matter of replacing the many by the one.

That the one who creates a single world out of many worlds is Śākyamuni Buddha is related to his being, as said earlier, both one and distributed throughout the cosmos. In other words, Śākyamuni Buddha can unify Buddhism and the cosmos, and therefore the life of the true hearer precisely because he himself is both one and many.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 182

Śākyamuni Buddha is, of course, the buddha of the sahā world. Thus, by elevating the status of Śākyamuni Buddha to cosmic superiority over all others, the importance of this world is also stressed. Here we can see one of the main themes of the Lotus Sutra, evident in virtually all of its teachings — the importance of this world and of life in this world. In this story it is to the sahā world that the Stupa of Many Treasures Buddha comes and it is the sahā world that is purified to receive all of the buddhas from other lands. The worlds of the other buddhas are described as wonderful in every way, but the buddhas leave those marvelous worlds in order to come to the sahā world and pay respects to its buddha.

In a sense, we may think that, since it is in it that the cosmic significance of Śākyamuni Buddha is revealed, praise for the sutra is always also praise for Śākyamuni Buddha. At the same time, because this is his world, praise for Śākyamuni Buddha is always also praise for this world.

The jeweled Stupa in which the two buddhas sit is a kind of tower and the character has that meaning in Chinese. The image of such a tower, surrounded by the buddhas and bodhisattvas from all over the universe, is clearly an axis mundi image. Such images always, I suppose, give importance and power to the place where the axis is located, in this case to this world and its buddha.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 181-182

[The arrival of the Stupa of Treasures] is a marvelous story, full of special imagery, cosmological in scope. But clearly such imagery is not so much for the purpose of explaining the nature of the cosmos as it is for extolling, first the Lotus Sutra, second Śākyamuni Buddha, and thirdly this sahā world.

Extolling the Lotus Sutra is both explicit in the chapter and implicit in the story. Many Treasures and the buddhas of the ten directions all come to the sahā world at least in part to hear the Lotus Sutra preached. In this way the Stupa is subordinated to the preaching of the Dharma. I take this to mean that the construction and worship of stupas and the remains of the Buddha are not rejected but are relativized, made subordinate to the Dharma and in particular to the Dharma expressed in the Lotus Sutra.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 181

The arrival of Many Treasures Buddha in his Stupa and the image of him and Śākyamuni Buddha sitting side by side are very significant… . The sutra emphasizes the fact that the whole body of Many Treasures Buddha, not just his remains, is present in the Stupa and that his voice emerges from it. But Many Treasures Buddha, we are told, had long ago passed into final nirvana. In this way the whole meaning of nirvana is called into question. And the sitting of the two buddhas side by side violates the assumption that there can only be one buddha in this world at a time. This is one of the ways in which the Lotus Sutra teaches that stories of entering nirvana are teaching devices to get people to be more responsible for their own lives, a theme which is developed most explicitly in the story in chapter 7 of the guide who conjures up a city as a temporary resting place for some travelers who want to quit the journey.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 181

Śākyamuni Buddha is praised for preaching the Lotus Sutra. Not only all of the creatures of this world and the gods in the heavens of this world, but even all of the buddhas of all of the countless other worlds in every direction also praise and subordinate themselves to Śākyamuni Buddha. Especially by designating the buddhas of the ten directions as his representatives, he is given central importance in the entire cosmos.

The Chinese term here rendered as “representatives,” but which might literally be rendered as “body parts,” has been interpreted and translated in various ways. It may be a reflection of the belief that one of a buddha’s supernatural powers is the ability to replicate himself. Exactly what is meant in the Lotus Sutra by the term is not clear. But one thing is very clear — all of these various buddhas, throughout the many, many worlds, are subordinate to Śākyamuni Buddha. Just how they are subordinate is not explained, no doubt because it is not important. What is important, given the priorities of the sutra, is the cosmic significance and superiority of Śākyamuni Buddha. Yet, at the same time, the reality or importance of those other buddhas is in no way denied.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 181

There are, obviously, many ways to read a sutra, perhaps especially [the Lotus] sutra! I take it to be primarily a religious text, that is, a text whose primary aim is soteriological. Whatever polemical purposes it may have served in some now unknown part of India in some now unknown community of Buddhists, the text addresses itself to readers, and to the salvation of readers, in any time and place. Looking at the text in this way will not produce a uniformity of results, but can lead to a certain kind of vision of this text as primarily an ethical text, ethical not in the sense of offering a theory of morals, or in the sense of offering a set of commandments, but ethical in the sense of recommending a certain way of life, a way of life guided by a single overarching purpose.

That unifying purpose is nothing less than the salvation, the happiness, of the entire world, a purpose rooted symbolically in the Buddha’s and bodhisattvas’ vow to save all the living.

To that end, the sutra utilizes several closely related themes, especially upāya or appropriate means, the One Vehicle, buddha-nature, eternal Śākyamuni Buddha, and bodhisattva practice, all of which, in one way or another, affirm the importance of this world and the life in it of the reader.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 178

In another extremely interesting passage [in the Perfection of Insight in Eight Thousand Lines], Subhūti asks about the meaning of the “great vehicle.”

“What is that great vehicle [upon which a bodhisattva rides]? … Who has set out in it? … Where will it stand?”

The Buddha answers:

“Great vehicle,” that is a synonym of immeasurableness. “Immeasurable” means infinitude. By means of the perfections has a bodhisattva set out in it. From the triple world it will go forth. It has set out to where there is no objective support. It will be a bodhisattva, a great being, who will go forth, but he will not go forth to anywhere. Nor has anyone set out in it. It will not stand anywhere.

The Buddha continues in this vein, but we may skip the text to Subhūti’s answer:

The Lord speaks of the “great vehicle.” Surpassing the world with its gods, men, and asuras, that vehicle will go forth. For it is the same as space, and exceedingly great. As in space, so in this vehicle there is room for immeasurable and incalculable beings. So is this the great vehicle of the bodhisattvas, the great beings. One cannot see its coming or going, and its abiding does not exist. Thus, one cannot get at the beginning of this great vehicle, nor at its end, nor at its middle. But it is self-identical everywhere. Therefore, one speaks of a “great vehicle.”

These ideas are extremely typical of the Prajn͂āpāramitā literature and may be taken as part of the formative matrix in which the chapters on the immeasurability of the Buddha’s life were conceived during the early phase of the development of Mahayana Buddhism. The key point to be learned from these passages is that “immeasurability” is part of a general discourse which seeks to indicate the ineffability of the true nature of things by disrupting conventional terminology. Whatever one can conceive of is part of the world as viewed by discriminating reason.

But the aim, in Mahayana Buddhism, is not to be entrapped by such discriminations. To avoid entrapment, the available terminology has to be used. But it is turned against itself. Thus a very large amount of merit is construed as being so large that it cannot be measured at all. And this in turn points to its “empty” nature, so that we arrive at the realization that a very large amount of merit is so immeasurably large that it is “no merit.”

It is submitted here that such an understanding of the term “immeasurability” underlies the usage in other Mahayana works.
A Buddhist Kaleidoscope; Michael Pye, The Length of Life of the Tathāgata, Page 168-169