Some of the highly militant vegans finds the Plant Life Colony Bubble and the few humans, also vegans, living in the food factory part of what's left of the colony. They insist that this can be fixed despite what the humans in the food factory try to explain, and learn the hard way WHY it can never be the way the humans had wished it to become.
Determination is ordinarily an admirable trait. Determination turns Vorax away from their raids. It drags injured friends across kilometers of wilderness just to reach a point where they can set off a rescue beacon. Determination cleans out hoarder warrens and restores a lost habitat to live-able condition.
Determination also sent aggressive Vegans back into the Plant Life Colony Bubble to fix the mistakes of the previous generation. They knew what they had done wrong this time.
So they thought.