alt Hacker NewsIIUC "FDIC insurance doesn't cascade into your customers' accounts" is not true in all cases, pass-through deposit insurance is a thing (https://www.fdic.gov/financial-institution-employees-guide-d...).
The problem in the case of Synapse was that they said they were doing that stuff, but were lying. (I think. The details of what happened there are apparently still not public. Also their bank seems to have been doing some sketchy things too.)
The biggest mess with Synapse seems to be the ledgers disagreeing: The banks, Synapse, Synapse's customers, and Synapse's customer's customers don't all agree on whose money is whose, and worse, the totals don't seem to add up.