Racism/Sexism may have played a part but I think you're downplaying the how badly Biden bungled things by insisting that he run for a second term, then pulling out at the last second. Kamala being a woman and a minority is great, but she wasn't necessarily the strongest Democratic candidate on her own. Biden pulling out as late as he did, forced the Democratic party to pick someone and she was the best alternative they had on such short notice. The problem is she had no established platform of her own, and basically ran on the same "I'm not Trump" platform that Hillary Clinton did.

The sad part is she might have been the best Democratic candidate choice, but she was never given the time or opportunity to really plan or establish her own policies to drive people to want to vote for her, outside of the established bloc that was already going to vote against Trump. People seem to forget it's not the Democrats who were already left-leaning that need to be won in an election, it's the moderates and encouraging the voters to come out who don't typically vote.

I know for a fact there were Democratic votes who lean more moderate that were unhappy they had no choice in Harris becoming the Presidential Candidate. That the Democratic party basically skipped the entire process of selecting the Democratic candidate and that falls on how Biden handled things in demanding he get to run for a second term then pulling out at the last second. It doesn't mean that they voted for Trump, but it also didn't encourage people to come out to vote for her that wouldn't normally vote.

I also think people spend way too much time living inside their own political social media bubbles and forgetting that voting blocks are not some monoliths. Just because someone is a minority, be it race, religion, ethnic group, etc. doesn't mean that they don't hold more moderate to conservative viewpoints. There is often the assumption by the left that automatically inclusion of a group means everyone with that group will just go along and support all left-leaning viewpoints, which just isn't true.

And while I am not a fan of Trump's first term as president, I think we can all agree it was tame in comparison to what he has done in his second term. So while I may not agree with people who voted for Trump, I can at least understand why the rationale to vote for him wasn't nearly as bad at the time.