The supply chain is long and fragile.

With interruptions in the provisioning of everything from the electricity required to parts for power management, cooling, air handling, networking, memory, disks, CPU, etc., the half-life of such centres would likely be on the order of a few years, even assuming local power.

Talent is probably the biggest factor.

Even absent greater civilisational collapse, a multi-billion-dollar-a-year income company such as Google can barely keep the lights on for a given project for 5-8 years, if that. Many startups fail even faster.