The decrease in value was due to exposure to long duration securities yes. The closure of the bank was due to a classic bank run after depositors panicked upon

The decrease in value was due to exposure to long duration securities yes. The closure of the bank was due to a classic bank run after depositors panicked upon hearing of the decrease in value. They had 45 billion in withdrawals in a single day, out of ~175 billion in deposits. No bank could survive that.