Maybe the way Nostr can get more people is by making it a good choice for semi-closed hyperlocal mini-social-networks, like a low-effort impromptu social network for a neighborhood, a church, a school...
this is how p2p bitcoin trading works too. nobody trusts a random app but if your friend says "hey this is how i buy" you download it immediately. local trust networks are the growth hack for every protocol that struggles with cold start