The Long Lines terrestrial microwave network eventually succumbed to changing engineering economics. Putting up microwave links, at scale, was cheaper in the mid 20th century than buying the real estate easements for cable trenches across the entire US. But eventually, the demand for high speed data exceeded the bandwidth available over the (relatively low frequency) microwave links. And a fiber optic cable has enormous bandwidth, making cable links the only viable way to increase capacity.

Ironically, microwave relays have recently been making a comeback in certain niche applications such as high-frequency trading, where the lower latency of radio compared with fiber is an advantage.

@mattblaze It's been a lot longer than "recently" - it's been going on for more than a decade.