This compares to the power grid or water supply in a given city, which are more of a natural monopoly. (Or indeed the railway lines)
If all the ridiculous permitting and attachment rights get sorted out, single-mode fiber is cheap and straightforward to install.
Take a look at any of the rural nonprofit fiber services. They’re not particularly expensive to build or operate.
I'm strongly in favor of capitalism, but deeply oppose the concept of privately-held utilities with local monopolies. No company should be able to "own the telephone poles" and have the last word on how they are used and by who. The poles, water pipes, gas pipes, sewer lines, etc, should all be owned by the municipality or county and vendors should have to compete to service and maintain them. There would be a lot of red tape, and plenty of room for corruption, but at least we wouldn't be starting from the position of, "oh, we can't have municipal broadband because that company a few states over owns all of our infrastructure."
They don't need gigabit internet but for large numbers rural residents even normal 25Mbps broadband isn't available.