I wrote about three paragraphs and then I stopped myself (I guess I'm a reasoning model), it's basically 3 things:
1.) The collapse of news networks/mainstream discourse after the pandemic led to further silo-ing of interests and politics
2.) Public perception that Democrats lost their Jon Stewart-esque libertine attitudes and that they're stodgy and judging, that they don't know how to market to people now who want "caught in the act/hidden camera" salacious stuff, they only know how to litigate it afterwards with reports and trials
3.) Oct. 7 is a big one I don't see cited a lot, while most people I know don't know about it, it's caused an internal division in the Democratic party of a magnitude that I've never seen before.