The wife and I were talking about this the other night. She's brand new to politics and didn't start paying attention until COVID when she realized that the government actually can play a huge role in the day to day lives of its citizens. She asked if Trump supporters were typical of Republican support for past presidents. I think the honest answer, being a former Republican myself, is no. And it has only escalated as the presidency moved on to the point where just talking about common decency is enough to get some dander up because I think a significant chunk of Trump supporters know, deep down, that they're being assholes to family and friends. They do so out of a sunk-cost fallacy. "I've been backing this position for 3 years. If I turn back now, I'll look like an idiot." So, they'd rather be an asshole than look like an idiot.
Then others take the all-in approach as a subconscious self-defense mechanism. If they are forced to question their judgment regarding Trump, maybe their judgment in other areas of friction in their lives was bad, too. They would have to accept that they lost friends and loved and they have no one to blame but themselves. Rather than do that, they cling to the belief that they're not wrong, everyone else that they pushed away was wrong. The majority of Trump supporters fit those two molds, in my opinion. They're all-in because they've burned all their bridges and there's no turning back or they're acting on a subconscious level of self-preservation.
Then you have people like my grandparents. Small town folk from a small town congregation that has been slamming the podium twice on Sunday and once on Wednesday for 30 years about how this country is trying to make Christianity illegal, outlaw prayer, burn your bibles, and kill babies in the delivery room. In their eyes, Trump is a clown, but they hold their nose and pull the lever for him because voting for a Democrat in their eyes means voting for the end of Christianity.