ThatZenoGuy
Residential Zealous Evolved Nano Organism
Fallout 1, you can tell the overseer to fuck off, then join the mutants, making them take over.
How\when do they destroy the wasteland ? Their goal is to convert people, not to kill them.
The master wouldn't have absorbed everyone. His goal was to save humanity, not destroy it. And the mutants scientist would have kept working on a cure to sterility. (which they did, but their labs got destroyed several times)
He absorbed beings at the beginning, but there is nothing to implie that he kept absorbing beings after he started the unity project.