The practice of "embrace, extend, extinguish" comes to mind with this. If Lemmy becomes 90% Threads then Meta can make huge changes to the platform. This would be a bad outcome.

I do like the idea of companies being able to host their own instance and join Lemmy, but I can't imagine that going well until Lemmy is already strong on its own.

I'm happy to be defederated with them, but I also have my (pure speculation-based) doubts about the platform lasting long enough to make a difference.