The question here isn't whether Threads will corrupt and destroy the Fediverse, the question is why does Threads exist? To corrupt and destroy the Fediverse is a nonsense answer. Why would Meta care about corrupting and destroying the Fediverse, which is extremely tiny compared to Twitter, Instagram, and Facebook?
You mentioned Fediverse support as somehow protecting Threads from antitrust regulators (a dubious notion itself), but there wouldn't be any need to protect Threads from antitrust regulators if threads didn't exist! What exactly is the raison d'être of Threads, if not to replace Twitter?
I know you love to bash Mastodon, but it's a red herring to this discussion.
The bare-bones launch of Threads seems to reveal Meta's priorities: the algorithmic feed, and the promotion of brands and influencers.