All depositors had $250k guaranteed at the bat. But sure maybe that’s short for 2 weeks of payroll for many companies.
Well FDIC was already cash payout warrants against the size of of their deposit assets (something like 50% would be available). If you need more than 50% of available cash to make payroll, you were already a dead firm walking.
With liquid assets like long term treasuries, they could have been liquidated quickly, and at worst most companies would have seen a 10-15% haircut.
A haircut hurts. But running a business includes all sorts of risks. You could have a lawsuit. You could have a fire. Your cloud provider could shutdown. They knew about the risk of being uninsured (since many companies have corporate treasurers who manage multiple banks and portfolio of treasury bills to manage bank risk), and this was just the one risk their company faced that came to fruition.