Why Did The Left Go Insane?

Here's a puzzling fact: the left went insane all at once.

   Of course that isn't true. But it happened fast--so quickly and on so many fronts that it was hard to keep up with. That seems to be a surprising / unpredicted fact--ergo in need of explanation.

If progressives had, say accepted transgender mythology, or moved toward open borders, or accepted social constructivism, or the intersectionality conjecture, or rejected free speech...some one of those things would be strange, of course, but more-or-less in line with the nutty enthusiasms that sweep both sides of the aisle. 

   But what happened was: all these crazy views and more swept through the vocal left all at once. 

   Progressives often try to argue that it was Trump--because, of course, everything is Trump. (Trump is everything. Everything and Trump are one...) But that's false. The crazification was already well-underway by the time His Obnoxiousness arrived on the scene. Trump was a reaction to the crazification of the left. He seems to have intensified it. But it's not clear by how much. It was already a runaway train before he had even emerged as the GOP frontrunner. 

   So what explains it? The crazy radicalization on so many different issues, that is?

   I've got hypotheses, various of which I've floated over the years...but, bottom line: I don't know. All I'm doing now is saying: it seems to require an explanation.