It's older than lockdown, though that accelerated it.
Personally, I think it's social media.
You get to broadcast your weirdest thoughts, and the algorithm explitly shows you people agreeing with you, and people you can feel righteous indignation against.
Which isn't social media per second, but is certainly how they all evolved.
Conspiracy theorists have always been with us, but they get an outsized voice.
Self-centredness and superiority complexes (and Dunning-Krugers) have always been with us, but the algorithms turn it all up to 11.
That leads to the likes of the tea party => MAGA, and the UKIP=>Reform, excusing and legitimising our worst impulses.
And the same on the left from "bleeding heart" => "politically correct" => "cancel culture"