I think the difference is the simplicity of the protocol, other protocols were too strict and complex from the start. Other protocols tried to keep banning and moderation control and tried to solve everything from the start. Nostr is more simple. Nostr also took inspiration from bitcoin, with the use of keys and nodes(relays).
Discussion
Yea, I was wondering if it was similar to Satoshi piecing together several different innovations to make Bitcoin. But it seems like it was more of a need to be filled and someone (fiatjaf) figured out how to do it.