[lsllc]

I think the implication is that anyone with an account so large it takes up the lions share of $13B probably has enough influence to make this sort of bailout happen:

  "Gee [senator|congressperson|etc], my donation to your re-election campaign was in that SVB account, would be a shame if I lost it".

[mrguyorama]

Or maybe american politicians have a long history of being buddy buddy with big money Capitalists, which most of SVB's clientele was, and had no qualms with throwing a few billions towards fixing a very local problem with the side benefit of helping their friends and another background benefit of reassuring whales to not pull out of other smaller banks.

Letting the whales die would have meant every other whale in every other bank would suddenly feel the need to inspect balance sheets or be whiny or just run. The entire reason SVB failed was poor management on their part, and poor risk hedging, but that's not a systemic problem. However, making every big cash holder suddenly worried they aren't as safe as they expected could be a mild systemic problem.