SVB could have bought 3-year, 1-year, 6-month Treasury bills with that money -- which during 2020 and 2021 were yielding <0.25%.

This would have been "safer", but lost them money.

Instead, they bought 10-, 20-, and 30-year T-Bills which were yielding more like 2-3%. Not much by today's interest-rate standards, but significantly more than 0.25%.

That appetite for long-dated bills could, I think, be described as "yield chasing." It was a decision made for short-term financial gain in ignorance of the risks involved.