85% of _deposits_ weren't FDIC insured, not accounts. Every account is insured up to $250,000 by the FDIC.

I'm sorry for the people in that position but it's a distinction with a difference.

Likely that Brex will loan you up to the max of your closing balance and 250K (the FDIC limit). Note that you need to link your account (so they can see your balance and transactions) to apply.

Right, so they aren’t guaranteed to get the money back, but SVB had large assets (likely enough to cover all deposits).

Those assets are year old long term bonds that have to be sold at a loss now (since interest rates are way up and brand new bonds pay better than these older ones).