If they didn't why would they develop tools to federate? It's obvious that the threads project was sped up significantly following musk's obliteration of Twitter, so they wouldn't go out of their way to implement such a feature if they didn't have a very specific reason for it.
A company's goal is maximization of profit, so don't assume they intend anything else. The activitypub userbase is too small to be a significant addition to their userbase but in this way they can destroy it before it escapes their control. They don't take risks. Mastodon could seriously compete with threads and it's gaining popularity. If one more big boom happens it might be too late to stop the fediverse from competing with meta in the most cost efficient way possible. Do not be lured in by the false sense of security, meta wants us to help maximize their profit. We aren't doing that right now so Meta wants to stop us (or limit us, whatever they deem more profitable)
Freedom is the goal with the fediverse, so I'd prefer it stays niche than become like reddit. I used reddit and now sadly Instagram too and the users can't be compared to Lemmy. Instagram is obscenely toxic, I will never doomscroll there again it was worse than reddit, which was also still pretty bad.
However what I really can't stand is the slow restrictions, the watering down of content to the point where it's insufferably bland. I came here to escape that. Post whatever the hell I want to post and browse whatever the hell other people felt like posting. The sincerity of everything is what makes the fediverse special for me.