The government's monopoly on punitive violence isn't only intended for the peasantry...
If you're not using your funding to support your goals, thats corruption.
People can vote that a new tax should be levied on billionaires, but can't vote how those billionaires will react to the tax. Moving out of state is one option (see Larry Page, Sergey Brin, etc). Hiring armies of lawyers to challenge any wealth assessment is another. Litigating to the Supreme Court yet another. I'm not a billionaire and never will be, but if I can think of these few ideas, they can think of 100 times more.
It feels to me you are asking "why can't we just eliminate billionaires". Well, they have a vote in that decision.
Considering the alternative for them over the past millennia has been, inevitably that they get caught, hanged, quartered, beaten and other various violent methods: yes, they should smile, they're buying their lives with all that money :)
Threatening violence to get what you want always ends with you being out-violenced by a bigger thug.
In humanity, being the alpha chimp, you can actually just run away from the tribe with all your wealth instead of outright die and form a new identity and start a life elsewhere and change your last name and go somewhere not well known, and if you and your family does this for enough generations you are forgotten.
I think this might explain the rotten apples at the tip-top of our industrial/societal wealth classes. I think they are these people, played out over generations, having somehow survived the system that used to make it impossible to do this when at the chimp level (or even medieval maybe, maybe this new form of evasion only arose in the industrial age).
And no, I do not believe that Musk's flabby arms or Bezos' shiny head are a threat of bigger violence to me anyways.
Extortion is the word that summarizes your point.
Just so you know, careers as a bootlicker are kind of a dead end.