A theory of (mostly) recent American history, by Bootstoots
America is normally ruled by rich white men. The majority of poor and middle-class whites still vote for rich white men, partly out of coming in the middle two classes of the American South's old class system, which went crudely like this: slave/overseer/white farmer/plantation owner. (edit: corrected per Lexicus' post below). Keeping the bottom two or three classes from uniting was a primary goal of the plantation owner class, and it's mostly been successful although cracks can appear in unusual circumstances, like parts of the South between Reconstruction and Jim Crow.
Anyway, rich white men like to party and behave irresponsibly. Sometimes these parties get out of hand. The snooty political family's mediocre son puts on a cowboy hat, home ownership gets underwritten by fraudulent loans and sold on to suckers, judges boof booze instead of just drinking it, a gilded con man/reality star/Twitter troll gets elected president, ... . You know, that sort of thing.
But all parties come to an end, and everyone wakes up the next morning with a pounding headache. It's like 9:30 am, and their last recollection was somewhere around 3, maybe? Maybe it was 2? Something like that. The boof guy is mumbling in a pool of his own...I hope that's just beer? Anyway, there's a lot of damage, and nobody feels up to cleaning up. Probably nobody even can clean up, beyond throwing a couple empty beer cans on top of the overfilled trash as they stagger out the door. They only have a vague idea of what a mop even is, and they're in no state to try to learn.
The white American people, the rich even more than the poor, then know it's time to elect the best freaking janitor ever. They're not going to clean up their own mess, of course, it has to be cleaned up for them. This is how a black president happens. The new president gets to work cleaning up the damage: taping up the windows and shopping for replacements, cleaning up all the booze and bodily fluids, mopping the floor another time to get what's left of that, donning Hazmat attire and cleaning the horrendous disaster in the bathroom, trying to dial the thermostat down because some frat boy dialed it up to 85 for whatever reason (only to find that it's actually broken entirely), and so on, and so forth.
He or she does a pretty good job. If the damage was serious enough, their contract might even be extended by another four years, and it's not even precarious and at-will! Finally, the wreckage is cleaned up and the house, while still having some permanent damage, is mostly okay again. This is when it's time for the rich white guys to come back for another party. And the cycle repeats.
Harris/Booker 2020.