Loading ...They don’t sell someone else’s shares per say they borrow them from a broker. Say a share is 20 dollars each they borrow it at that price. Then say it drops back down to 10 dollars and they give it back at 10 dollars and keep the profit.
So there’s no profit in holding it not selling it. But if buying pressure comes in and the shares instead go up in price say to 30 dollars depending how much money or cash they have will dictate the price the broker demands a margin call it now cost more. So say he has 2000 and he just lost 2000 in the difference and moves up 10 dollars they have to pay the broker the 10 dollar difference. But now if your black rock or vanguard and have infinite amounts of money they can choose hold longer. Then theres naked shorting and how they get away with that and never have to cover I don’t know.