So, a short squeeze is a real thing. The stock going up means that the people holding an underwater short need to rush to buy to close their positions before they go farther underwater. This then makes the stock go up faster. That's indeed what happened last week.
But you don't need to buy back all the stock, just enough such that you have enough flexibility to hold the stock across the inevitable peak and drop. In a consumer brokerage, this generally takes the form of a "margin call" and the brokerage will often buy stock for you out of your margin so they don't get caught holding the bag, and eventually can seize your whole portfolio to make themselves whole (the regulations there get complicated and I'm not expert). It's an absolute thing, and you lose all your money. But that's not how it works for a hedge fund, the nature of which is to have access to financing regular people don't. They can just cut a deal with bigger players to get through, and that's how Melvin seems to have managed this.
To be clear: Melvin made an outrageously inappropriate bet, got caught, and lots a ton of money. But they're out now and the story is over. Now GME is just a bubble like any other bubble, fed by naive investors believing it will go up when it won't.
As far as "what happens if WSB doesn't sell?", the answer is nothing. WSB doesn't hold the full capitalization of GME. There are plenty of other shares out there being traded, and the price of those trades is what you see on the ticker.
> some say they are, some say they aren't. Is this in fact true?
The ones which said they are out are out. There isn't actually any evidence that they stayed in. There is a lot of frenetic speculation on reddit that they're still in, which is mostly the result of redditors cargo culting bad "game theory" to support their own priors that hedge funds will always lie no matter what. I have written many comments about this in the past couple of days; suffice it to say that these conspiracy theories are based in basic trading illiteracy and misunderstood jargon, mixed with a heavy dose of emotional investment.
On the other hand, there is good evidence they actually closed out when they said they did: the hedge funds getting burned when GME was at $50 and $100 simply wouldn't exist anymore when GME hit $300, $400 or $500. They would have been margin called and it would have been game over.
And finally - yes, some funds are short GME right now. But that's not because they were short at $4.5, it's because the current price is dissociated from reality and all the smart money wants to short the peak.
It's hard to say because every source I can find shows institutional ownership is 120-160% and I don't know how it's possible to own more than 100% of a thing. I suppose that could all be the short positions leading up to the recent drama.
Stock creation of this form is not entirely unlike the money creation that happens with fractional reserve banking. A short squeeze is crudely analogous to a bank run with that mental model.
(I have no market position on any individual stocks... because I don't consider myself sufficiently well-educated to do it. So take that grain of salt as you see fit).
But you don't need to buy back all the stock, just enough such that you have enough flexibility to hold the stock across the inevitable peak and drop. In a consumer brokerage, this generally takes the form of a "margin call" and the brokerage will often buy stock for you out of your margin so they don't get caught holding the bag, and eventually can seize your whole portfolio to make themselves whole (the regulations there get complicated and I'm not expert). It's an absolute thing, and you lose all your money. But that's not how it works for a hedge fund, the nature of which is to have access to financing regular people don't. They can just cut a deal with bigger players to get through, and that's how Melvin seems to have managed this.
To be clear: Melvin made an outrageously inappropriate bet, got caught, and lots a ton of money. But they're out now and the story is over. Now GME is just a bubble like any other bubble, fed by naive investors believing it will go up when it won't.
As far as "what happens if WSB doesn't sell?", the answer is nothing. WSB doesn't hold the full capitalization of GME. There are plenty of other shares out there being traded, and the price of those trades is what you see on the ticker.