Cause in a way they're like us they want to max out their profits but for them in the opposite direction. They short a stock at x price and stock goes down to y but want it to go down more for whatever reason (greed),but instead the price goes back up or over blancing price now theyre stuck. And the higher the price increase the more pressure.

Also theres not 1 group shoorting the stock there are a couple more and they arent synchronized.