Gamestop isn't something Economic theory really covers. They don't tend to pay much attention to the implementation details of the underlying market apparatus, so the various dynamics that occur around shorting shares, price pressure when the position is closed, naked shorting, etc. aren't something they think a whole lot about.

Keynes was ok for his time on the banking system, and made a fortune on foreign currency trading, but HFT etc. was a bit before his time.