The reason why this happened is that their clearing house stopped fulfilling their orders (totally out of their control,) but Robinhood bungled this so badly, I honestly wonder if they'll ever recover. WeBull had to do the same thing but they have a clear reason rather than "protecting investors" etc.
I do agree Citadel, which I believe helped out one of the hedge funds in trouble form the short squeeze, being the clearing house is a "moral hazard" and a conflict of interest.