His speech patterns and dialogue match up surprisingly well with Jim Jones of the famous Jonestown Massacre. Once somebody like that has a following, it doesn't matter how crazy he gets, the diehard believers will literally die hard for the guy.

The first campaign drew the cult together from a cult that was already there (a groomed voter base who will vote Republican no matter who) and the first term bonded them together against an enemy (everybody with common sense) while the Republican party and the entire media insulated them from how bad he is. There were some people who saw what he did and turned away - he got less votes this time around than he did last time, and that's even with the questions of election interference that keep cropping up - but that just means that the people left are the crazies who would defend him even if he personally started shooting up schools.

American politics is so screwed up that most people have little clue of what exactly happens in this country. A coworker of mine just the other day was effectively saying that daddy Trump had to hurt us because big-meanie Biden ruined the government deficit.

Because they were told that Trump would protect them against all of the bad things that Trump's backers were blasting into their brains 24/7 via social media and partisan 'news' organizations.

Ignorance and disinformation did way more work that Trump's charisma which is, as you've said, lacking