I assume banks went ahead and bought subprime mortgage bonds with that $300B. And at this point why not? Everyone knows that the government will print an unlimited amount of money to keep the system going no matter what risks you take and how careless you are.
SVB and Signature banks both failed , their shareholders walked away with nothing. This does not encourage risk-taking on the part of the banks.
In that period, your excessive risk taking will likely show excessive growth, which will likely lead to stronger stock prices. If you’re a banking exec, your salary is linked to stock performance. You can easily run up 5-8 years before the whole edifice crumbles, pocketing fat bonuses in the interim.
Who cares if Joe Shareholder gets left with nothing at the end? You and all your exec buddies can make off like bandits in the interim.