Mastodon isn't trying to compete anyway, it's not a Product(tm) driven by desire for profits, so the people who use it don't care if it "wins" or becomes more popular than whatever other platform. We're all just hanging out socializing and stuff, sharing neat things and discussing things like communities do. It's not easy to accurately estimate active Mastodon/Fediverse users, but then again, I'm not sure anyone really cares either way? lol