Maybe I can help clarify. Citadel doesn't own RH. Citadel has two arms, separated by regulatory rules: Citadel the asset management group (HF for our definition) and Citadel Securities, which is an option and stock market maker (depending on your age, think the guys standing on the floor buying and selling for customer orders). Citadel HF doesn't (or shouldn't) have anything to do with this current situation.
RH is a different company that offers an app giving small retail traders the ability to open an account for very little money and have free trades. RH makes money two ways 1) selling trade order flow, mostly to Citadel. So an example, a person does a trade, RH sells the trade to Citadel Securities who executes the trade and makes $0.01 to $0.005/share (bid-ask spread) and gives back some of that money to RH. Second way, is lending the securities (Sec lending) they hold for clients to traders who want to short and need to borrow (yes, the irony here is almost laughable).
I will leave it there to keep from getting too complicated, because there are a lot of other connected pieces, but that is the gist of it.
I'm not a fan of RH's decision to not allow trading in some securities, but I have to admit that they can see a much larger picture that I can. The biggest problem for them is that a client holds a $200 strike call expiring tomorrow. The stock closes at $250 and that client needs $25,000 to buy those 100 shares the option was worth, but they may not have that amount in their account. The broker assumes the responsibility. The option can just disappear and piss off the client or might be auto-exercised the broker needs sell securities on Monday to cover the client's shortfall. It might open Monday at $100 given the craziness we have seen. The broker assumes that risk so they are trying to make sure clients can cover themselves.