Chose to exceed that and also not diversify at the same time. In my mind they have only themselves to blame. They could have gotten one or two more accounts if they are legitimate businesses.
If they had deposited that 3B in, say two banks rather than one, they'd have 1.5B in that other bank
Use treasures bills if you’re that concerned.
-Purchase high-limit cash insurance from a Reinsurer like Lloyds of London or Berkshire Hathaway up to their underwriting limit, perhaps $100M. Do this across 4-5 different banks with 4-5 different reinsurers.
-Put the remaining $2-2.5B into mixed US Treasuries of varying maturities
If your entire business model revolves around moving multiple billions of dollars via an asset-backed stablecoin model, it's reasonable to expect you to have dozens of bank accounts, in at least 3 time zones, and likely more.
I don't know why people (not saying you specifically) seem to have this expectation any entity should be able to deposit billions of dollars risk-free at a single institution.
Ironically it's often the same people who can intuitively grasp why to hold your crypto across multiple wallets, who cannot fathom that infinite $ cannot be deposited at a single bank, without risk.
If you're leaving 7 to 9+ figures in a single account, then either buy custom insurance, or only do business with banks which offer excess insurance.
People here simply decided to not inform themselves or seek appropriate assistance and therefore got bitten