system
Given the following post, respond as if you're commenting on Reddit:
human
[Planet of the Apes]Why did the underground mutated humans not take back the planet? Clearly they were strong enough though their powers of illusion/telepathy.
gpt
the radiation from the bomb was the source of their mental powers.  in ancient times some mutant humans had tried to retake the planet, and succeeded in conquering isolated areas, but without their god their powers weakened in a generation and they were exterminated.  these occurrences did of course exacerbate ape-human antipathy, but in modern ape society stories of such were taken no more seriously than we do tales of witches.

the other reason of course is that their numerous mutations made breeding difficult, many children were born with virulent cancers, many of the mutants were sterile and barren.  Indeed their society had been much larger but was in a slow state of attrition, with their population falling every century.

mutant society was also quite insular and against outside exploration.  there was a deep and prevalent cultural fear that any members who left would inevitably lead the hordes of apes to them.  while their mental powers certainly gave them *an* advantage over the apes, the apes' greater strength, ferocity, and  most importantly their massive populations would have easily overwhelmed the small and isolated mutant community.

*disclaimer; i haven't seen any of the planet of the ape movies.  most of what i know about the series comes from a mad parody of them i read like 20 years ago, so most of this is made up from whole cloth.