US Treasury Bonds are one of the safest investment vehicles, IF you match the interest and maturity to your liabilities. You cannot go and buy bonds that will mature and give you 1% per annum in 10 years when you have a debtor awaiting payment in 90 days. That's the huge risk mismanagement SVB did.

Having said that, I don't think startups will suffer big time - but they were the ones also who created the bankrun fueled by VC panic. However mismanaged SVB was, given enough time they had enough resources to turn this around.