Fiber wouldn't be a one-time charge though. There's regular ongoing maintenance needed for a fiber network.

There's an old joke in the telecom world:

Q: If you were going to be stranded on a desert island and you could only take one thing with you, what would you take?

A: I would take a small bundle of fiber optic cable. As soon as I was on the island, I'd make a small hole in the sand and bury it. As soon as I turn my back there would be someone with a backhoe there to dig it up.

The cost of sending crew out to fix a 10 mile fiber run servicing a single household would wipe out any possible profit from that subscriber for more than 100 years. Now multiple that by how many 10 mile+ fiber runs we'd need to service all those widespread low-density rural customers.

Those satellites are all earning profit everywhere else around the world they can service. That line to a 100 person community taking decades to be profitable is money the ISPs dont want to spend because it'll take decades.