It's got pull for developers. It's open, it's friendly, it doesn't cost money to develop for. It has some monetization built in. For example, Dave bot is already 'profitable' I heard. Twitter shit itself by kicking off the developers, many of which helped Twitter become so popular in the first place by offering useful services and information programatically. Nostr opens up many innovation avenues simply by being developer friendly.

It's also got pull for bitcoiners. Not to be underestimated, as Bitcoin grows, nostr naturally will grow also.