“Evolutionary reason” does not necessarily mean that a feature is an advantage. Mutations are random and then positive or negative selective pressure act on them untill the mutation is either extinct or is adopted by the whole population. For features without selective pressure the same thing still happens it just takes longer and is basically random. So different populations of a species will always develop different features even when given the same environment.
So for most of the features you listed: yeah it just happened.
Great game, really nice visuals and nice (very trippy) soundtrack. I tried to be a “good” cult leader, trying to ressurect everybody that “died” (most got sacrificed before they could die of old age), but some people should stay dead. And mourning and sadness is just another reason to put everybody on shrooms again