Comment by ajkjk

Large scale divergence in the two human moralities: social morality (rules for people around us to protect the community, largely coded liberal) and personal morality (moral intuitions for how to keep you and your immediate family safe). The two have become at odds with each other so everyone feels intensely and uncompromisingly threatened by those who ascribe more to the other, leading to two groups that can no longer even 'treat with the enemy' much less collaborate on their mutual preservation. This was aided along by a whole lot of largely unchecked fearmongering because it turns out that that sells views, clicks, and ratings.

(and possibly also a general dumbification of everything due to bad education combined with lowering social standards for who is allowed to have a public voice and be take seriously; confusingly thus was one of the points of a standard of decorum, because it served as a filter on who was intelligent enough to be a thought leader.)