Perhaps in some cases, but the venture money deposits could be used collateral for loans, giving the startups access to even more capital. So the bank was draw

Perhaps in some cases, but the venture money deposits could be used collateral for loans, giving the startups access to even more capital. So the bank was drawing in startup clients with these nontraditional loans while requiring that they deposit the venture money with then for surety. It wasn’t just coincidence that they were so disproportionately in one sector and had such a share of uninsured deposits. It was their strategy. It just backfired when that venture money tightened up, and finally blew up when the money spooked. People are focusing the TBill thing thing because that side of the story broke first (and was amplified by VC PR) and glosses over the part that implicates how the startup sector was using them.