As my wife puts it, there's no reason to look for conspiracy where things can be explained by plain human stupidity. It's not Putin, or Xi, who broke U.S. politics. It's the stupidity of people who vote, which goes from bad to worse while manipulation techniques - driven by arms of race of ever more brainwash-y advertisements, in a market of enormous volume, easy measurement, and vast leverage for the winner - get better and better by the day.