You are not referring to intelligence itself but to what having or lacking nurture looks like from the outside. Actually, no unhinged society of sociopaths comes to mind. That's a fantasy example, not a real one.
Back to the topic: Low intelligence societies can have favorable cultural and nutritional nurturation, but this doesn't cause an increase in the population's intelligence among its select individuals. Over time, in a world of changing conditions, we'll see such a well nurtured, low intelligence society eventually loses out due to its inability to solve various group-affecting problems that happen along. An organized high intelligence group can enter their habitat and out compete them in different ways. They can also obliviously Easter Island themselves out of existence. So much for a time of nurture, which relies on extrinsic variables, for a low intelligence group.
They'll thrive sustainably for a long time when the following conditions are met:
- where the climate is warm or body warmth is easily manageable with low tech
- they remain out of contact or are protected from contact with modern industrial civilization
- where other human competitors are scarce due to regional low population density
- where protein sources are readily available all the time
- they are able to migrate away from worsened ecological conditions or resource scarcity