I don't think all disagreement in politics lacks greater substance, but a lot of what is presented as "centrists nobly fighting the left" is really about one faction of people, and their outriders in the broader political-media-consulting industrial complex, being worried about being displaced by people aren't supposed to be there.
It's not their place. They might trash it!
It's about their pals losing their status and power and all that comes with that (including the friends and family jobs networks).
This is most obvious in the reaction to Mamdani. Sure a lot of it is racism and generally insane pro-Israel people, but nobody not insane or bigoted thinks he's going to install full communism and Sharia Law. He doesn't even have the power to do those things even if he wanted to, given the powers of the NYC mayor.
Did all those people who supported Cuomo think he would be a good mayor? Of course not. But they thought he would keep the party going for their professional networks. They thought he would, mostly, keep the right people in positions of power, keep the pecking order at parties the same.
I don't think everyone is purely cynical. I think many people in their upper echelons of the US cannot fathom that anyone outside their little networks is competent. That's bad, but not precisely the same as calculated corrupt cynicism. It has the same result, though.