You are papering over the fact that even cash accounts require Robinhood to have sufficient cash to cover amounts liable until the trade is actually settled. There is an entire web of relationships between DTCC, robinhood, bank LOCs, etc. that make robinhood's capital requirements explode when GME stock explodes 1000% up and becomes the most traded share in the entire universe of stocks.
In a volatile market - a single share may trade many times a day - and Robinhood has to have enough to cover each trade (not share) - so the market cap is not a ceiling. It's likely RH didn't have enough money to adequately cover the levels of volatility (or they projected they wouldn't, soon).
Apple alone had a volume of 170M on Friday, for a total of $0.9B cover required, GME had 50M or $10B cover needed at ~$200.
There would have to be an insane ratio of meme-stock trading vs SP500 for GME alone to impact their cash requirements - if that’s the case it seems they dug their own grave...
