I am not so sure either. It is not a singular event or action.
See my post here
The deposit flight has started much earlier. Many folks have recognized bank deposits are paying way below market rate and started moving their money. The deposit flight from banks into money market, treasuries started when the rates crossed 4% and it seems regulators have spotted the issue with SVB, but not intervened strongly earlier.
Separately, Raghuram Rajan, former Central banker of India, Chicago booth school professor, had a paper out on this asset-liability mismatch and potential issues, looks like FED didn’t read that paper or didn’t take it seriously!!!