Threads should be Lemmy compatible. So in that sense Facebook already has an instance. The result is that many instances blocked them right away.
In the end I think this will all grow organically. Some companies might opt to host their forums on their own Lemmy instance. But that shouldn’t keep other instances from having their own communities about the same topics. More or less like it already is today.
And there already is drama with the non-commercial instances. People will gravitate to the communities they like and stay away from those they don’t. That should always be the case.