If you've discovered this secret why aren't you out there rasing venture capital to start a bank?
This is not a secret, John Law practiced this 300 years ago. Commercial bank do not have right to create money, only central banks can. Just look how FED and other central banks' balance sheet exploded while they acquire large amount of assets since 2008
So what if their balance sheet expanded? Still has nothing to do with them "buying the economy"