I used to live in middle-of-nowhere central WA, and they had fiber internet all the way back in mid 2000’s. This was a town of <20k people. Other smaller towns around the region also had access to fiber as well. Basically it worked like this: the county public utilities district was responsible for laying the fiber and connecting it to the building. Once the fiber is hooked up, you can call any one of a dozen or so ISPs to provide you with service.
As a side note, because of this relationship between the ISPs and the public utilities district, some ISPs also operated point-to-point wireless networks to reach customers outside of the fiber network. The ISPs would typically place a tower with several radios at an existing customer’s site, in exchange for free service. These tower sites were usually connected directly to fiber for minimal latency. I mention this because I don’t see how these wireless networks would have been viable without a public fiber network backing them.