> GME exposed how undercapitalized they were...

Or, more accurately, the extreme volatility of GME led to increased collateral requirements that Robinhood couldn't meet. (It was like billions of dollars, iirc.) Or, otherwise, it's not that Robinhood was undercapitalized (or even is undercapitalized!)—just that the goalposts moved suddenly and unexpectedly.

PFOF is still a little squirrel-y. Ditto on Levine and others, and tied up in all that T+2 settlement issue, too.