His advice wasn't bad though. He said if you believed in it form the jump and still believe then hold.
There is no fundamental reason why GameStop will stay up 1,000% regardless of your beliefs though.
Put another way, this is like buying a PS5 and paying black market prices because retailers are out of stock. If you need a PS5 desperately, right now, it makes sense, but when you decide to sell a PS5 in six months, the immediacy/hype around PS5's will have died down as will the price gouging. You cannot pay top dollar when every is really interested in PS5's and then expect to sell your PS5 for the same price when people aren't as crazy about PS5s
The exact same principle applies to the stock market & GameStop stock specifically.