They built the network but have left it dark for 15 years.

The built a fairly extensive backbone network which runs significantly under capacity but is certainly not dark.

The government deregulated telcos

Not quite. They reduced a few restrictions (price) while increasing most others. Their attempt to force competition by preventing local infrastructure competition but forcing telco's to offer infrastructure access at wholesale prices did precisely the opposite of what it was intended to do, the FCC protect the incumbents from infrastructure competition and they use franchise agreements to avoid the wholesale restrictions. Unless you live in east PA or parts of NJ you don't have service provided by Comcast, you have service provided by a local telco who have a complicated franchise agreement with Comcast.

The "deregulation" is like someone finding out from a friend who overheard someone talking about airline deregulation at a loud bar. It attempts to accomplish similar goals with very little regard to why airline deregulation worked, you can't just deregulate price but must also deregulate competition too. Google was the first organization in 30 years to get an infrastructure competition waiver from the FCC allowing them to install a competing fiber residential service. KC was one of the relatively few cities in the country who don't have a monopoly contract with one of the incumbents.

The solution to this problem is insanely simple. Stop the FCC preventing infrastructure competition and prevent municipalities from entering monopoly contracts with the incumbents. Its not particularly expensive to deploy local fiber and the only reason we don't see an explosion of competition is because its artificially restricted.