to tease out the nuance, the mechanism of mainstreaming isn't an extension of stupidity (ignorance is certainly a more accurate term), but of limited focus and stress. most people don't spend much time thinking about the wider world and how it should work very deeply, so they follow the herd on most things, because it's a decent heuristic and it has a social benefit.

it's a literal luxury to have enough time and mental space to think for more than a few minutes on any given issue. that's one of the most valuable "legs up" that wealth gives you, not so much the money itself, but the room to think (and unfortunately, often to try to manipulate the world around you in a self-serving/self-centered way--the corrupting of personal integrity that's as old as time).