Republicans had 8 years of Clinton, 8 years of Obama, and 4 years of Biden to see how Democrats govern. So they know what they will get. Anyone who says but Kamela will be worse is rationalizing.
So what drives them?
First there is a large segment that truly do want the old days. They want white men in charge telling us all how to act. They want Christian religon in school. They want the government not telling us or protecting us for liberal ideas like equality. They want the government forcing conformance.
There is a great book, American Nations, that I highly recomend. In some of our cultures people believe they should do as the elites direct. In some poverty in return for minimal government involvement is a good trade-off. These people are a sizable chunk of the populace and they weigh things out very differently.
Second, there is a chunk that is racist, mysoginistic, and/or nihlistic. For them, they want someone who hates what they hate and validates how they view the world. And these are the fundamental values of these people and in a democracy they get a vote – same as all of us (no one said Democracy is a great system, just that it sucks less than all the others).
To me the big problem with this group is we have a ton of young men growing up alienated from society and they find their fellow bros in these groups. They don't see a future from themselves with a great job, family, etc. and so they go into this cesspool. We need to find a way to reach & help any of these we can.
Third, there are the single issue voters. If you believe that human life starts at conception, that a 2 celled organism has a soul, then abortion is the critical issue for you. If you believe that we will see the end days in the next 20 years, then strip mining makes sense.
Or a more pedantic note, there are people that are all about their tax rate. You can explain that Harris will double the value of your stock portfolio over the next 4 years, Trump will half it, and they still will vote on the possibility that Harris may raise their taxes 2%. People hate losses more than the celebrate wins.
And there you have it – 45% of the voters.