The ones in power are the ones holding the coins, and the coins can be created by literally anyone on the planet out of thin air. The price going up doesn't force diehard fanatics to sell. This is where HODL culture comes from. If central banking tries to buy out crypto that's going to make thousands of the smartest libertarian (anti-government) cryptography experts on the planet billionaires. What do you think these people are going to do when their coin becomes co-opted? They'll make a newer, better coin, that is even harder to buy out.
Fiat is powerless. Fiat is dead tech that hasn't evolved for 100 years. No one is going to want anything to do with it once the tipping point is reached.