During the 1990s dotcom boom we massively overbuilt fiber networks. It was indiscriminate and most of the fiber was never lit.

After the dotcom crash, much of this infrastructure became distressed assets that could be picked up for peanuts. This fueled a large number of new startups in the aftermath that built business models figuring out how to effectively leverage all of this dead fiber when you don't have to pay the huge capital costs of building it out yourself. At the time, you could essentially build a nationwide fiber network for a few million dollars if you were clever, and people did.

These new data centers will find a use, even if it ends up being by some startup who picks it up for nothing after a crash. This has been a pattern in US tech for a long time. The carcass of the previous boom's whale becomes cheap fuel for the next generation of companies.