They did already have 77% of the collateral in short-term T-bills, and the 23% in cash was spread out across multiple banks. They held $3.3bn at SVB, but that's out of $42bn total.
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.