carnage4life, Mastodon founder, Eugen Rochko, praises Threads entry into the #Fediverse because it makes Mastodon “a far more attractive option.”
This is fairly obvious and basic network effects since both Threads & Mastodon become more valuable as their users can now share content across these services seamlessly.
This angers Mastodon admins for whom the fact that not a lot of people use Mastodon was a selling point. They do not want it to grow and be useful to more people.