I suspect what happens over time is this, over and over:

1. A developer on some non-nostr system finds nostr and recognizes it for what it is
2. They move their system to (or bridge into) nostr
3. Their userbase is now added to nostr, so nostr suddenly gets a lot more users

Sure users will come over seeking certain kinds of content, but I don't expect that is the main way that nostr will grow.  It will grow through acquisitions.