I know quite a few people I would call "damaged Christians," who have left their church often not of their own accord. The number one reason is a family breakup. Typically, one side gets to keep the church and the other is tossed out. There is still a lot of fault-finding in divorce and other family issues in these churches.
The second big cause I have seen, especially with the mega-church folks, is the crash of the minister (sex or financial scandals, for instance) or a personal falling out with the minister. You can see years of financial and personal investment go up in smoke.
In both cases, there is a forced confrontation of the person's core beliefs different from a seeker who drifts away because of a better understanding of science and history.
In the above two cases, I have often seen the "bubbling under the surface" biases re-enacted: racism, sexism, etc. These people are pissed, as opposed to the seeker who left for intellectual reasons.
My sister-in-law is a case in point. Her husband was a bit too weird for their Fundamentalist church, and they were shown the door. They still consider themselves Christians, but see the church as one more corrupt institution, and want them all to come down. Thus, Trump.