IIUC part of the reason ballistic missiles have multiple warheads is that some of them detonate high up to knock out air defenses and other electronics allowing the rest to fall through to their targets. The last time we tried this experiment as a species was the starfish prime tests in 1962 which caused some electrical havoc in Hawaii. These days our systems are probably more delicate and sensitive? All that is to say, in a scenario where nukes are going off I'm not sure you'd even need to target any datacenters in particular.. they're probably all toast by default.