What happened to Silver Gate is completely different than what happened to SVB and Signature. So I'd separate the two problems. The first one was crypto, so I put Silver Gate into the same camp as FTX. You live by the sword, you die by the sword.
SVB and Signature were relatively well-run, well-capitalized banks that both made the same, significant mistake. So I don't want to minimize that, but it's not like 2007, where you had issues where banks had no idea what they were sitting on. In this case, you can readily see this problem on a balance sheet.
Both banks had a ton of cash deposits they were sitting on, and they bought bonds, in many instances, long term (10 year) gov't bonds at 1.5%. Nice and safe, right? Well.... yes, when interest rates are at 0.5%. But this is where the risk management people at these banks dropped the ball. In 2021, interest rates were still low, but with inflation rearing its ugly head, the Fed started raising interest rates, and relatively quickly. I don't blame the Fed too much (although they waited too long to start, but that's Monday morning QBing), but with inflation approaching 10%, they couldn't be too slow on the rate increases. If Fed interest rate is now at 4.5%, holding onto a 10 year treasury with a 1.5% coupon rate isn't all that great. So SVB's ability to sell those bonds to generate the cash for their depositors daily cash flow needs (payroll, etc) got expensive, because they could only sell 10 year treasuries on the market for about 91 cents on the dollar. So , a 20 billioni dollar sell of bonds was going to cause a loss of $2 billion.
This isn't good, but it does happen, and a bank will typically sell additional stock to raise the capital needed. But their messaging was poor, several big VCs got their panties in a bunch, and you had a good old-fashioned, "It's a Wonderful Life" run on the bank.
Why SVB couldn't find a buyer with cash is what's causing me to scratch my head. If I'm Buffet (Berkshire Hathaway), siting on top of $85 billion in cash, I stroll in, buy a significant piece of SVB for pennies on the dollar, and make an extremely tidy profit. Why he or someone else hasn't done that is what's making me concerned. What do they know that I don't know? (likely a lot)