It's not any one group shorting that much. It's just that the aggregate has shorted that much.
And I'm not sure that it really matters that the shorts exceed the total stock available. Because it's not like everyone will have to cover their shorts at the exact same moment. An entity can buy stock to cover their shorts, then the entity that received the stock to cover the "uncovered" position would then be free to turn around and sell that stock again.
The real risk would be having a super large short position for a stock that has very low volume since it would be very difficult to cover lots of shorts if there aren't many people selling stock.
And I'm not sure that it really matters that the shorts exceed the total stock available. Because it's not like everyone will have to cover their shorts at the exact same moment. An entity can buy stock to cover their shorts, then the entity that received the stock to cover the "uncovered" position would then be free to turn around and sell that stock again.
The real risk would be having a super large short position for a stock that has very low volume since it would be very difficult to cover lots of shorts if there aren't many people selling stock.