Nostr also has the excellent cost-control mechanism of first requiring users to set up a cryptographic key pair - you can smell the freedom from here! - and second of being full of coiner spam. This keeps server usage to a minimum in practice,

well, precisely. Banks expected depositors would keep their money in the bank. This turned out to be incorrect when interest rates went up.

So basically, Signature and Silvergate did. Their problem was not crypto directly, but crypto customers - they had billions in deposits which didn’t stay in the bank, the customers kept withdrawing huge amounts at short notice like it was their own money or something. Neither bank could quite cover the deposits at such short notice, and eventually they just died. Both were kept working in that time. Silicon Valley Bank went down soon after in the same way, except the hot money depositors were VCs and startups.