I wonder if politics is a top line issue or a bottom line issue. Teenagers never seriously paid attention to politics when I was a kid, now everyone does. So are people really getting dumber or are dumber people getting into politics.
Talk radio and then cable news really ushered in the political entertainment era where what matters most is whether a story feels right for a narrow audience, and then the internet provided the amped up version. I wouldn’t say dumber as much as provocative but once the ad-tech engines started rewarding hot takes they became predominant.