SVB and Signature Bank failed after 2 looming risks went against them — and many other banks are facing the same fate.

Silicon Valley Bank and Signature Bank failed with enormous speed — so quickly that they could be textbook cases of classic bank runs, in which too many depositors withdraw their funds from a bank at the same time. The failures at SVB SIVB and Signature SBNYwere two of the three biggest in U.S. banking history, following the collapse of Washington Mutual in 2008.

How could this happen when the banking industry has been sitting on record levels of excess reserves — or the amount of cash held beyond what regulators require?

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