SVB bought long duration bonds, they could not wait until maturity to get the money back. Keep rolling short duration bonds would be less risky.

The interest rate risk of a 10y t-note is a couple orders of magnitude higher than the interest rate risk of a 1 month t-bill, because of duration.

USDC would have to wait just over a month for all of their t-bills to mature, SVB was looking at waiting 8 years.

Massively different risk profiles.