Because a) he's a Russian asset (apparently) and b) they have incriminating evidence on him and probably a bunch of other billionaires. Also, if they could spend a few billion in return for control of pretty much they would, they'd be willing to pay for it.

Billionaires dont care as long as number go up.

They can’t be that incompetent

Have you seen these billionaires? They absolutely can. The myth of their competence is pure propaganda.

Also, they like corruption because it offers many opportunities for those with enough money to pay. And they like oppression of workers because it provides a ready pool of cheap labour to exploit.

They'll be looking at Russia and liking what they see, because they don't see themselves being the ones working for pennies and being sent to die in Ukraine. And they all think they're the smartest guy in the world ("why else would I have so much money?") so they don't see themselves being fucked over by Putin either. For them Russia is the promise of doing whatever you want, taking advantage of whomever you want, and getting whatever you want.