Robinhood Is Said to Draw on Credit Lines from Banks Amid Tumult (bloomberg.com)

Robinhood's instant access to transferred funds is a margin account feature. So is instantly having access to your funds from selling a position. So just holding one share of GME increases RH's liquidity requirements. When I asked why the company I work for didn't do the same I was told we couldn't afford to give every warm body a margin account.