I can only speak about Bitcoin here as I'm not as familiar with how other coins work. Bitcoin is basically designed to make this hard.

In order to spend money you need the private keys. No way around it, even with 51%. What you can do with 51% processing power is rewrite history. You start a parallel chain where the oligarchs never received their money. When your chain accumulates more processing power it will in theory be accepted as the canonical chain. Now there are a few problems here. First the simpler one: If you want to rewrite any significant amount of history, say undo a transaction from a year ago, you will need more than 51% to achieve it in a reasonable time. Think of two runners, one is a few percent faster, the other has a year long headstart. It will take very long to overtake. With 66% of computing power you can do it in a year*. Renting that much power for that long year would be extremely expensive. Second problem. It's highly doubtful that people would just quitely accept such a huge rewrite.

* Assume the rest of the chain has processing speed X. If you have speed 2X then it works out to 66%. One year of 2X power equals two years of X power, catching up with the 1 year headstart.

Sure, just link your bitcoin node to my network and we'll take them down together. I promise I wont use that to steal anything other than Oligarch crypto, which I also promise I can identify 100% accurately. You can trust me.

They will need to deposit some of their bitcoins to the attack nodes wallet as well. The more we have in their the more oligarchs we can take down.

Might just as well put millions of dollars on a picture of a monkey then resell it once you're out of Russia

We shouldn't use the word theft here, think of it as mining some oligarch coins.

I'll keep that in mind if I ever have the opportunity to empty your bank account.

I don't have any crypto that can be mined by a blockchain vote AND I am not sending any armies to attack Europe.

I don't see how that's relevant. Most of the Russia oligarchs aren't either, and blockchains aren't the only computer security mechanisms that can be overcome.

Its not emptying their bank account its mining pawelmurias coins.

We are seizing ill gotten gains, not stealing.

You say tomayto, I say tomahto.

51% attacks can only block transactions, not undo them or fake them.

They can undo previous transactions / blocks, but it takes a lot of work (the older the block the more work it takes). For recent transactions (last block) it may be practical, that's why 6 confirmations are advised for high value transfers.

It can also corrupt state if the target clients are light (and only verify headers).