Are you aware of Mostr: a Fediverse Nostr bridge? This enables Nostr clients to communicate with the fediverse, which already has millions of users.
In addition, Ditto is also being created to support both Nostr and Activitypub protocols on one platform.
Edit: I see what you mean now actually, I don’t think nostr will last as a go-to social media platform or a place other than to ephemerally exchange information but I actually think that fits.
All-in-all I think GRIN needs to be brought to the masses through “normie-friendly” spaces as well. Nostr isn’t really normie friendly.