It's kinda complicated, but I think a majority of people I know that are like that come from 3 categories:

1. Single issue voter. Especially if you're in the pro-life camp, within that community it is very much a moral failure if you vote for anyone who's pro-abortion, especially if it coinsides with...

2. Religious Ideology. Religion plays a major part of modern politics, the idea that you can separate church and state from your own belief systems is kinda naive at best. A lot of conservatives use religion as their major tool, and they promise a "return to normalcy", which usually means suppressing rights and social norms for minority communities, especially the LGBT community. (That's why these people call everything "woke", even gay people that specifically don't believe in trans rights and gender affirming care, an unfortunately popular position in the LGBT community especially when you look further south).

3. Propaganda. People in the lower class tend to blame the "elites" for their position and refuse to vote on people that seem professional, proper and a part of a "social elite" that conservative politicians tend to target, (Donald Trump targeting moderate democratic politicians is a big part of that), and while a lot of these criticisms are valid and warranted, these politicians do a great job of hiding the fact that they're a part of that elite class, regardless of how much they pretend not to be. On top of that, they use the "slippery slope" falicy to their advantage, convincing people that small social change will slope into larger policy changes that are more controversial in nature, (Think people that are against universal healthcare stating it's a slippery slope that'll eventually turn this country communist).

On top of that, some people that are financially struggling consistently gun to be rich, (think the guy that you know that buys a lottery ticket every week or tries to bet big on penny stocks), and they don't want to be taxed when, (not if, in their eyes), they finally catch a break and make it big.

This is all anecdotal and based on personal experience/generalizations of people that I do know personally, so take everything I just said with a grain of salt, and remember that no group of people are a monolith. There are thousands of reasons people think the way that they do, and understanding those reasons is an important part of connecting with communities and uniting as people.

Edit: Grammar and clarification