NASDAQ is a market maker system. That means that every single company listed on the exchange has one or more 'market makers' who guarantee liquidity for that stock. The set their bid and ask prices and guarantee some volume of stock is available at that price. While they try to match every buy order with some seller and vice versa, if they can't, they themselves will buy the stock into their own inventory or sell it from their own inventory. The difference between bid and ask is their profit, and it's usually tiny but with good volume, they still make plenty of money.
But when you get to a volatile stock like GME, that can get dicey. GME is seeing jumps of $20-$40 in a second. There is the very real possibility that a market maker could get caught in a series of trades that either deplete their entire inventory of GME, and hence, make it impossible for them to guarantee liquidity, or simply start losing so much money so fast as prices jump beyond their spread that they cannot buy stock once they run out of liquid cash on hand.
There are also some legitimate risk reasons as well, but risk is also where the shady reasons come in. And given the fact that GME has become a straight up attack on a short sellers, if a market maker is one of those short sellers (secretly...cuz ya...that's a no no), or they're simply really good friends with a short seller, or they've invested into a short seller's hedge fund...