You are correct that it existed well before, the difference is that it was always complicated to use. Heck, we have been able to send PGP emails since almost 30 years ago.

The innovative concept is that npub/nsec along with sending notes is trivially simple. The content does not need to encrypted, there is a huge value on publishing clear text messages that are crypto-verifiable. You also didn't had this feature on groove and others. I'd argue that NOSTR has indeed pioneered them into mainstream.