Note: I said hoarding billions - I didn't say they're hoarding it in literal cash. They're hoarding it in value.

Inflation is beneficial if you have billions in value because what you can earn from interest rates and valuations (especially when you can tug at the strings of the stock market) alone will exceed what the inflation rate will be (barring economic collapse where there's runaway inflation, like the Weimar Republic or Argentina).

This means that your purchasing power goes up since the general population's and smaller business' purchasing power goes down, since you can easily outpace inflation far greater than they can. This allows you to hoard more wealth by making it easier to buy up other companies or stocks - and the more you own, the easier it is to ensure that you control the general population's wages or the growth of competitors and therefore increase your wealth further by staying even further ahead of inflation. If you're an American even remotely paying attention to things, you might realize this cycle sounds familiar.

This eventually hurts the overall economy if never stopped of course (lack of general active cash flow), because eventually things become too unaffordable for the general population and they can only take so much debt... But if you and your cohorts keep at it, thanks to how the fiat system works, it's fine. Because you'll own so much of everything and have so much value hoarded that it doesn't matter that inflation has crashed everything and your currency has lost significant global power, since you'll be able to buy up anything else left that you don't own (Btw, this isn't hypothetical - this is how Putin and his cronies gained what they had, at the expense of a whole country). From there you and the oligarchs can basically run the government.

And that's the big picture most people miss - it's not about the money, it's about power.