They aren't loaning money to the startups (well, mostly). They handled the banking. This current problem has nothing to do with their clientele, it has to do with long term bonds.

They sell banking services to startups... all companies need some way to manage payroll (for example). Regardless of the balance sheets of their clients, they should have been able to manage assets such that they could fulfill day to day banking needs.

It's that failure to manage assets on the bank side that we're talking about. Startups/clients failing should be a normal event at SVB, given their focus.

As far as I understood it, the 10% which paid off made SVB into the type of bank it is today.

They obviously made a bad move in 2020-21 in thinking the public market was going to crash and what would happen to bond yields, but so did lots of people.

If you think SVB is the only bank which is making high risk decisions to get payoffs, I would suggest you level up and look at what ALL these banks are doing. Faith in the system and long-term risk assessment isn't built into the mentality of banks which have so much invested in equity trading vs. boring deposits.

The financial stability of the depositors had ~0 to do with this situation.

This is completely wrong. This was a classic bank run caused by the startups banking with SVB switching from net depositors to net withdrawers as they aren't able to raise in the current environment and obviously none of them actually make money. The withdrawals start, there was a liquidity and then a panic and boom bank dead.