The bank was caught off guard on two fronts:

• VC money slowed which caused new deposit balances to slow,
• they were also expecting startups to slow their burn rate (and so slow the need to draw down on balances) more than what has occurred

Selling their Treasuries at a loss to meet the higher than expected customer demands for their funds rekt them once word got out they needed to raise money to cover those losses

I find second point the most interesting, means still a lot of companies with high burn rates who may also get rekt as this thing works its way through system