> The companies building out capacity certainly believe that AI is going to use as much power as we are told.

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.

It's not future demand, it's current demand. Microsoft has already said they're power blocked rather than chip blocked.

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".