Most people seem to have been led to understand that the short leverage of 140% meant that when the short call happens, the hedge fund will "have to buy more stock than exists" to settle, and thus that something like an infinite price spike will happen. The same people tend to refer to this as a "naked short", which it is not[1]. Most of these people seem to have latched onto a theory that the short calls are all coming due today and that they NEED to buy as much GME as possible ahead of the metaphorical rapture.

But the hedge funds in question closed out their short positions days ago. The stock right now is being propped up by simple (and misinformed) speculation. And effectively all of the purchase price that people are paying right now is going to end up being transferred to the people with earlier positions who are getting out at the peak of the bubble.

[1] A naked short is a short sale where no underlying stock was borrowed first. This is a crime, but only possible for certain very privileged traders with control over the various tracking records. Leverage over 100% just means (for example) that you borrowed a share, sold it, then later went to the same buyer and borrowed it again. You end up owing them "two shares", but not necessarily the same share twice. In practice what happened is that as the stock started rising, Melvin closed its position buy repeatedly buying and returning shares to the tune of 140% of the capitalization. (Edit to add: it seems likely that it did so in combination with a bunch of loans and favors from other hedge funds with the ability to buy and hold GME across the inevitable collapse. The WSB folks complaining about hedge fund corruption and insider dealing aren't wrong.)