If they get a margin call it's done automatically. Broker starts liquidating all their long positions to begin covering short positions. Price shoots up from that. Triggers margin calls on other accounts with same short position. And same long positions for that matter.
Sell offs to acquire cash for covering will tank those long positions for others which then increases their margin ratios on top of SP spike for short positions. It's a domino effect similar to what started WWI.
Liquidate is not necessarily belly up. Successful long positions can be liquidated to cover failed short positions. Does this drop several other stocks? Yep. Some HFs abused pandemic conditions by shorting pandemic SLR exemption. Justice is a bitch. If Citadel doesn’t have long assets to cover their entire short mess then yes they do go belly up....but their creditors are on the hook. These creditors will then be forced to liquidate long position to pay for Citadel toxic short bets.
At some point does the system collapse because they are too many toxic bets? Probably but we aren’t there. The10 year treasury bonds went negative, meaning the “stable” bond market is going to get rocked by this Citadel mess....bond investors will NOT get the yield “promised”, but investments won’t go to zero.
Lots of guessing in a complex system, but IMO AMC squeeze is an unavoidable train wreck created by SLR exemption ABUSE.
April 1st is going to be a sh!t show across the entire market.