Could someone please explain how Proof of Stake is still decentralized? Seems to me that any scheme that puts the control of what gets written to the blockchai

Could someone please explain how Proof of Stake is still decentralized? Seems to me that any scheme that puts the control of what gets written to the blockchain in the hands of entities heavily invested in it allows for the possibility of token value manipulation. Simmilar to an IMF intervention created fiat currency crisis. Doesn't it create insiders out of all proof of stake holders without the protections of the SEC for everyone else holding a lesser stake? Maybe this is true of all crypto regardless of methodology.