There is literally no evidence that Citadel has stopped serving GME orders. That is entirely the conjecture of this thread and ignores the much more likelier option that it was Robinhood that limited the stocks.
Why wouldn't you short GME after the price has risen so high? I'm sure there are plenty of hedge funds shorting now at a much higher price.
Hell, I shorted AMC yesterday and have made quite a bit off of that already.
Because the stock is already over 100% short and an army of retail investors is purchasing it
Because that is also often when it is a good time to make money.
It's entirely unsurprising to me that short pressure on the stock would increase after this.
The risk to a company that processes trades is that many of these retail investors accounts would turn negative and the company that processes the trades would take giant losses they did not plan for. To prevent that, they stop processing trades.
Today, there is still a 122% short position on Gamestop. There are still many funds hedged against GME. Melvin might have had one of the larger positions, but there are many more funds with this position. Source: https://finviz.com/quote.ashx?t=GME
As you say, they would make money by running the orders, regardless if GME goes up or down. So - why would they stop? It is most likely that Citadel is still exposed to other funds holding short positions in GME.