The problem is the lack of a coherent framework of rules that correctly apply existing constitutional principles to modern technology. The 4th amendment should have been sufficient to prevent the casual destruction of the concept of privacy, but it's become overwhelmingly apparent that we need an explicit framework protecting individual digital information rights. Make commercial surveillance illegal, or prevent mass harvesting of private data, and you've solved much of what's fundamentally wrong with big tech.
Problems with Facebook, et al, are symptoms of bad legislation. By focusing energy on "fixing" the companies, we risk losing sight of the institutional failures that allowed them to become a problem.
Now you've given the other two companies more of the market share. Not only that you've given them time to lobby and protect themselves.
So you've now reduced competition even more.
You are trying to fix the wrong problem. The problem is the market, not facebook.