The US economy depends on you trusting that your bank account is less likely to disappear than a pile of cash under your bed is.
That's why the US government steps in for one case and not the other.
There is also precident for the government to pay damages above insurance limits after natural disasters, which from the depositor's point of view this basically is.
From what I understand: SVB offered below-market rates on loans and even personal financing for the founders of companies if you, in return, use them exclusively as your bank and put all your raised capital into an account with them.
You buy favorable rates on loans with the increased risk of putting more than the insured amount into the account.
When your house gets damaged in a flood and you've selected to insure it for $250k because that's cheaper, and you've knowingly built it in a floodplain, is the government still going to cover 100% of the cost of building it?
That's why the US government steps in for one case and not the other.
There is also precident for the government to pay damages above insurance limits after natural disasters, which from the depositor's point of view this basically is.