Sunk cost fallacy for a lot of them, to be honest. I’ve heard people criticize his big policies (trade war, trying to be isolationist and etc.), but still say “still better than what the alternative could become”.
The other side of the aisle did not do themselves any favors with the "bitter clingers," "basket of deplorables," or "hell yeah, we're gonna take your AR" type comments. That was all red meat that fed right into people being able to radicalize folks into "vote for Trump, or the other side is coming for you and your way of life."
People on the right were literally calling 2016 a "Flight 93 election," i.e. "storm the cockpit before they can fly this plane into the Capitol," and it was because they feared Hillary would nominate a Supreme Court supermajority that was the opposite of what Trump did, and that it would bury their way of life. You can agree with this or think it's horseshit, but either way you still have to start by understanding that it's what many voters believe. The dismissive condescending comments that Obama and Clinton got caught making, combined with the backlash to George Floyd being murdered in the form of riots and extreme left-wing viewpoints getting aired fed straight into fears in red states that they were going to get bulldozed unless they struck first.
