Crowdism

[prime]

We find that whole communities suddenly fix their minds upon one object, and go mad in its pursuit; that millions of people become simultaneously impressed with one delusion, and run after it, till their attention is caught by some new folly more captivating than the first.

https://www.gutenberg.org/files/24518/24518-h/24518-h.htm

I have never read this, but it looks like a riff on Nietzsche:

"In individuals, insanity is rare; but in groups, parties, nations and epochs, it is the rule."

Crowdism is the idea that human groups naturally tend toward insanity by converting to rationalization as a thought process, in order to avoid mention of fears/taboos as a way of holding the group together. It is a codependent mutual denial of the reality of fears so that a pleasant bourgeois mental state can prevail.