This is my working theory as well. There are socio-economic factors that were in place long before Trump, but the nationalist / fascist talking points have been drilled into these people's heads for the last 50 years or so. Limbaugh's screed starting peeling away what little common sense many of them had in the early 90s. Those that weren't already racist / bigot shitbags have been more-or-less Pavlov'd into hating everyone other than themselves.
Then along came shitstain. A fucking conman grifter whose life is the American Dream in a mirror darkly. These people have been howling for Limbaugh and Hannity to run for office, and then this fucking troglodyte comes along and actually does what Ma and Pa Conservative want: he runs for President on the most vile political platform since Charles Lindberg and America First. He says all of their quiet parts out loud and they love him for it.
But there aren't another 80 million GQP musketeers waiting to join in the fellating of their new savior like they've been told. Turns out, a majority of Americans want nothing to do with this shitheel. They cannot hold or consolidate power through the massive nationalist movement they were promised because the other side is so vehemently opposed to their batshit insanity as if to be a part of another reality. Cognitive dissonance, for some, hurts their brains. So they pick their side, willingly leave reality, and decide that if they can't have the America they want, then they'll just burn it all down.
The only endgame for most of these folks is death or prison; they have no real governing ethos that goes beyond the short-term. They don't even know what they really want, other than to make folks that don't look or sound like them to suffer. If a global pandemic and a fucking botched overthrow of the government wasn't enough to wake these people up, nothing will.