Much ink has been spilled about "Evangelical" hypocrisy when it comes to Trump. Of course these are not real Evangelicals but a version of Fundamentalism--I digress. Here's a column from Michael Gerson contrasting Billy Graham's reaction to Nixon's scandals with Graham's son's open embrace of Trump.
But the best explanation I have yet read is this one which identifies the roots of this form of American religion in the slave-holding South and a break-away from actual Evangelicalism which was abolitionist. Excerpt:
patriarchal amoralism, not the Bible, not Christian teachings, is the foundation of this Evangelical sect. After slavery, it justified the lynching of blacks, segregation, and the vile hatred that we see being fanned today in such churches. Being patriarchal and authoritarian, it has never in America’s history supported nor nurtured the values of democracy. Thus Its “religious” leaders convey the theological values needed to prepare its communities for fascist rule. This thread has always existed within American society. It is not new. It is not superficial. It will not disappear. America made a moral compromise at the beginning of its existence. Every century or so, the reality of it gets thrown like acid into our faces.