The same could be said of dark fiber laid during the dot com boom, or unused railroads, etc. Spending during a boom is not indicative of properly recognized future demand of resources.
Please note how I say current demand, and don't over project as to what my opinion about future demand is. I think there's a small, but reasonable chance that demand will sink for some reason or another in the next few years, and I think there's a pretty decent chance that in the next five years someone will come up with some way to make these things an order of magnitude or more more efficient, which would crash their electricity demands. But it's not a hypothetical "we need power in two years", or at least, not just that... it's we need more power now.
There's a big difference between "I may hypothetically need some more capacity later, I'd better go buy it now" and "I concretely need more capacity right now".
This is not me doubting you, but your comment will carry considerably more weight if you provide a reference to Microsoft's statement.