Your own example, Bell System, is an example of an sub-optimal but obviously adequate regulated monopoly that worked moderately well over a century.
Ummmmm, no.
Whatever your economic viewpoint, there's no credible way you can claim that the Bell monopoly was healthy for the economy. This is the same organization that had to be taken to court to allow new devices to be plugged in. Remember these? https://en.wikipedia.org/wiki/Acoustic_coupler They weren't built because it's more efficient for computers to communicate over soundwaves.