Why assume FB would kill an acquisition? They didn’t kill WA, IG or Beluga. They made them into massive billion+ DAU services.
But people like short videos, so there's a tension there. If you're in ads, maybe just buy a few short video companies, get their patents to sue their competitors, and shut them down, so no one gets access to the thing that they like but is less lucrative for you.
But maybe you're right and they would have followed an IG model just fine.