Simple: the people electing him are racist white southerners.

Those kids in the 60s treating their new black classmates like shit, the white teens pouring drinks over black teens doing soda-counter sit-ins, the young white couple that’s all smiles as they attend a lynching… they didn’t just poof out of existence when the Civil and Voting Rights Acts were passed. They grew up, had kids that they taught their racist bullshit to.

And all of them vote.