Simply party politics (and identity politics which is sorta the same thing).

Those who believe Trump is bad can generally not explain WHY they think he is bad,….he just is. Because.

And those same people, many of them otherwise reasonably intelligent, will vote for Kamala Harris. They have to know she is a train wreck, and a total mess, and a person who they normally wouldn’t let organize the garbage cleanup from a school bake sale…but because she has the imprimatur of whoever is the power in the Democrat party they will vote for her for President. Because (D),

There are some possible candidates on the DNC side who, while I disagree with much of their philosophy, I would have confidence in as President and leader of the country. …..but none of them are named Harris. There are many good reason NOT to vote for her.

Ultimately, we are left to make the choice between the least bad of the two candidates.