Internet is a necessity for participating in the modern economy. So, companies that provide it, particularly when they hold a monopoly or are part of a duopoly, wield a tremendous amount of power; or, maybe even worse, when they have a strong enough hold on a given region but opt not to provide broadband to some of their service area, making it nearly impossible for some rural folks to even have broadband. They've shown themselves unworthy of being trusted with such power, over and over again. It's unfortunate that legislators in NC are complicit in that abusive behavior.
It would be ridiculous for them to waste any money by investing into their infrastructure unless it enables them to compete better, increasing revenue and profits.
They are acting in exactly the way you'd expect given how the economy is designed. The problem are the rules politicians have setup which are designed for a free market not for monopoly/duopoly situations. The only option you have here is realistically is letting local government provide internet.
This way internet becomes part of the services municipalities provide and they compete with each other in being an attractive location for businesses and citizens, so they're incentivized to provide good and cheap internet. At least as cheap and good internet as other places anyway.