Because the area is controlled by the US Forest Service, and if you want to get “high real estate” in that area, you need to negotiate with the Feds.
One of the issues when you’re seeking to site some electronics or antenna up on a mountaintop is “is this a pristine area?” If there is no one else already there, then your application will likely face a much tougher road than if you’re applying to site your antenna on a mountaintop where someone already has an antenna, power and buildings. In many cases, the stations might be using their own antennas, but their equipment is all co-located inside the same building, with the same power feed and backup power generation systems.
I hope there is some emergency alternative broadcast site. Having all TV go off the air at once will stir up some folks. (I guess cable feeds will not have a problem.)