Well, I don't work for Threads or Meta, and I don't know anything about their short-term or long-term plans. But let's imagine a theoretical, commercially-operated social web service called "HeartStrings", which acts in bad faith:

• HeartStrings uses their significant marketing ability and existing user base to become a dominant entity in the Fediverse. Simultaneously, they downplay or even hide the fact that a lot of their initial content comes from the Fediverse. This isn't difficult as their traditional target audience probably won't know about the Fediverse or even be able to understand the concepts behind it without significant explanation, which they are unlikely to pursue on their own.
• HeartStrings implements extra services for their users which only work on HeartStrings (karma, useful built-in bots and moderation tools, regular prize giveaways, "preferential" positioning of posts from HeartStrings, their own spin on "hot" or other post sorting options)
• They create local "backups" of posts from other instances (a.k.a. scraped content), "for the convenience of HeartStrings users" and, initially, also as "a service to the Fediverse."
• Once they have sufficient users and content, they begin blocking posts both to and from certain other instances (probably not actually defederating, but handling everything silently, internally). When someone finally notices this systematic censorship, HeartStrings provides vague justifications involving "misinformation" and "illegal activities".
• Because this creates minimal backlash from core HeartStrings users, the company works faster and faster toward their end goal of completely removing ActivityPub support while simultaneously implying that the Fediverse came to HeartStrings (rather than the other way around), was given a fair chance by HeartStrings, but turns out to be filled with terrorists, drug sellers, pedophiles, and other bad actors. With no central body to defend it effectively against such a well-financed aggressor, the Fediverse takes this virtually without responding.
• Result: HeartStrings has sucked what free material and promotion it could from the Fediverse during its critical launch phase, then sabotaged the Fediverse, and finally kicked it to the curb.