Global machine pub/sub seems interesting. Transaction/psbt signing coordination is developing. Shortwave was the old way to get a message heard across the globe. Now it's machine readable via internet.

Why weren't people doing it before nostr? Well, the network of relays is important. I think nostr makes it easier by boiling it down to signed and broadcasted messages. There may have been ways to use email or some other relay network to accomplish the same thing, but maybe not so simply.