For buried infrastructure where the coaxial cable company already sells internet, you will almost never recoup your investment to bury new fiber and run it to all the homes. You can have the superior product, but insufficient people will pay enough more than the existing coaxial cable prices.
Probably a main difference is that the Swedish infrastructure was deployed by municipalities with an open access model, so no need for 10 different ISPs to dig their own cabling.
I got underground fiber direct to the basement of a student apartment years ago and it was basically a hundred dollars for install fees. They must have already been laying it on the street, but still. Competition?
As a result, many rural areas have way better internet than big cities.