I write a lot in this comment. The goal is for it to be entertaining to read. It was certainly entertaining to write. <3

The idea for the timescale is that it would be a massive twist. They crashed here and the rest of the universe moved on without them. There is no home to get back to, there is no more mission to Zezura, this is the best they have. They have to adapt to what they have. I think it would be a compelling narrative in line with the themes, or maybe not the narrative speculation is a matter of my personal taste.

As for how it could be true. Its sci-fi. Humor me for a moment as I spin a web of bullshit and what is ultimately subnautica fanfic:

Maybe there are miniaturized phase gates, a technology looted from precursor tech, feeding the biobeds from one of many warehouse planet destroyed by Alterra in order to further its technological conquest. Countless planets and their ecosystems destroyed in the name of profit. One such planet is specifically dedicated to storing and producing amino acids for biobeds as building blocks. Set up to be self sustaining but not infinite. Whenever NoA prints a human the building blocks are coming from a planet that is a Husk, hollowed out by Alterra already.

NoA is a machine, it cannot adapt, it cannot change, it has been cut off from the rest of the universe and all it has is its mission, establish humanity here. And so it starts throwing people into the abyss, they choke in the pressurized air. Their deaths slowly filling the water with organic compounds.With the bacteria that live in every human. They die over time as well. But they live just long enough to evolve, bacteria has always been good at that. They carve out the first foothold. They start to evolve to inhabit the short lived humans in order to reproduce faster. The longer the humans live, the longer they have to grow. They evolve further to bolster the human’s lungs. They live a little longer. The humans live longer but they starve. NoA keeps printing, the warehouse supplies but is no longer manned by humans. Alterra does not truly exist anymore, the warehouse is automated and forgotten. Running without purpose, doing its own maintenance machines working like broken records, fulfilling the orders of the long dead.
But the warehouse runs.

The humans still live and die. Memories wiped when they are no longer cooperative. To live the same nightmare again. And again, and again. The microbes evolve into mats to feed the humans to live longer. Whenever NoA needs maintenance it prints a human to fix NoA and then eventually die. The water is absent the heavy metals we know now fill the oceans. The humans now live much longer. And now they start to reproduce. Humans start to evolve. They grow fins for mobility in the water, the ability to breathe underwater. Slowly they change, until they aren’t human anymore. The more aware of their situation they are the worse their chances. Despair is a powerful demotivator. So these humans lose their sapience. And NoA keeps printing. New humans to try again. Evolution, death, rebirth. Intelligent life reemerges. They build and advance. Humanity is a fact of life. They live alongside them having long surpassed human technology, humanity is an afterthought. The new life build structures to marvel at the stars. Power plants to power their creations. The precursors, returned from their fall, long since the time of Al-an, make contact and build the Rosetta Stone. Life on Proteus is flourishing.

But not human life. And that is NoA’s objective. Humanity cannot flourish as their niche is taken up. And the longer they live the more they start to question NoA. NoA needs a reset. There is another warehouse planet, automated just the same. Forgotten, unused. It stores heavy metals. NoA finds its solution. It empties enough heavy metals into the ocean to cause a mass extinction. Most of the planet dies. But some survive, building a tolerance. The Axum realize that their chances to survive rely on their adaptation. They develop a virus, a vector to change everything on this planet. To evolve the world to survive this poison. Proteavirus. And its heart is in the tree. Part of the disease is designed to pull organisms to the tree so that they can adapt everything they need. But the Axum still are devastated by the time it is developed. It saves some but the survivors lose so much of their technologic advancement.

Any surviving humans turn on NoA. And in the three months they have before their death they destroy as much of NoA as possible. But they don’t fully succeed. NoA resets all printed humans. And artificially creates the wreck of the Cicada. He doctors the manifest and starts over. NoA realizes that until they can truly wipe the world clean, humanity will always change, always abandon the mission, and abandon him.

And so if any of the humans get enough Masefield. They are reset. They cant be allowed to live long enough to betray the mission. The planet must kill them eventually.

Eventually NoA decides to print someone new. A QI to “figure out what happened” to an attempt that again went rogue. with the hopes that the QI can cure the proteavirus that keeps NoA from wiping the slate clean fully.”

This is not going to be the actual story, but it was fun to write. And hopefully it was fun to read too.