The managers of this bank were supremely stupid about how they managed their exposure to interest rate risk. And by “supremely stupid”, I meant that stupidly held a sizable amount of their interest-bearing assets in longterm government bonds. When interest rates spiked due to the Fed moving to slow down the economy — and rein in inflation, the bank’s bond portfolio lost a LOT of value, especially so for a bank that had over 4/5ths of its deposits not protected by the FDIC $250,000 limit per depositor, something like $150+ BILLION. Those kinds of deposits are SUPER sensitive to any whispers of a possible problems with the bank’s net worth, which is why the bank so quickly experienced a devastating bank run.

In essence, those idiot bank managers would get an F in my Financial Institutions course for such a massive fuck-up.

Addendum: Their unprotected deposits were over 90% of deposits, $155B out of $173B. So, yeah. Effing stupid.