This specifically comes down to two elements, IMO: outright grifting, and being reflexively opposed to established centers of power (and the corollary: being far too invested in one's self-perception as a brave, truth-telling outsider).
Don't get me wrong: a lot of established centers of power are really awful! But if your whole identity politically is unflinching opposition to 'the establishment', it's really easy to get led down the garden path of finding common cause with others whose identity is unflinching opposition to 'the establishment', even if those others are just the worst people in the world. Glenn Greenwald still thinks that he's a brave truth-teller as he's carrying water for Tucker Carlson, and a depressing number of purported leftists have had similar flirtations with the extreme right, because of their shared interest in blowing **** up.
The second, even larger problem is that it's basically impossible to govern; that'd make you the establishment, and then you'd have to make compromises and difficult decisions and all the things you are critical of others for doing. So it's much easier just to play the Purer Than Thou game while also sabotaging those who share 90%+ of your aims, because then the superiority of your agenda can remain purely theoretical.