You are right of course, but we've established a moral hazard

There will be a cost to suddenly altering expectations, I guess there's a chance we might see what that cost is now (but probably they will just get a boring bailout)

No we have not established a moral hazard. It's always been $250k. You are trying to make one up implying that we are "suddenly altering expectations". The narrative has always been, FDIC insured accounts are insured up to $250k.

I've known this since I opened my first bank account.

It's a moral hazard if people over 250K got bailed out in the past. Look up the Temporary Liquidity Guarantee Program.