For starters, many of the counties that "vote for the Republicans" are like 60-40 or 70-30 splits, so somewhere between a third and a half of the people living in those areas voted Democrat. And of course, many don't vote at all if they know their state is locked in for a given candidate regardless.
Second, there are myriad issues that due to America's 2-party system ultimately get grouped into relatively arbitrary bundles. If you have to choose between two bad options, you might choose the one that's less immediately bad or less guaranteed bad or less severely bad, even knowing that the alternative is future-bad, maybe-bad or slightly-bad.
Third, just have sympathy for all people in all walks of life. Especially the marginalized. You likely don't have an understanding of their day to day struggles or how those inform their decisions and coping mechanisms, and even if you are right and they are wrong, please take a moment to consider how your privileges may give you the education, time, energy, resources and context to come to different conclusions than other people.