I thought about this thread while I was reading this article. It is a review of three books detailing the source of the current state of the American right.
The first book (_A World After Liberalism, Matthew Rose) is about the intellectual underpinnings of the right; how various racist and ethnocentric thinkers going back all the way to Spengler developed ideas that appeal to many in the west who resist cultural and demographic change. Despite their lack of a mass following, their concepts found followers who could put them into operation.
The second book (The Right, Matthew Continetti) shows how the more mainstream conservative movement yielded over time to the demands of its most radical and antidemocratic members, citing the end of the Cold War as when whatever commitment was left to small-l liberal democratic norms began to be discarded. The reviewer points out that Continetti believes the conservative movement strategizes based on the support of the radical right without truly realizing the degree to which the tables have turned.
The final book (Why We Did It, Tim Miller) details the psychology behind why Trump was able to take and reshape the Republican party in his own image - or the image of his radical right supporters in whom he sees his reflection. Miller, a gay (former?) Republican political operative, tells about how some of his fellow politicos made the psychological switch to accommodate and ultimately embrace Trumpism as a lesser evil than the liberalism.
I don’t know that I’m going to read any of these books, but I certainly recommend the synopses in the linked article.