If they're building new power plants to support all those data centers than that power generation capacity might be put to good use doing something else.

Lots of ifs going on here. I haven't been so optimistic of tech this decade compared to the early '10's.

As global society we must strive to reduce energy consumption, not to find new use cases for burning more energy. Our planet has limited resources.

The data centers themselves with all the supporting infrastructure (telecom/power), as well as all the chip fabs needed to build the hardware, even if the hardware itself becomes obsolete / breaks down on a 4-5 year time scale.

In the same way the rights of way obtained with all the railroads were, even if the rails / engines themselves had to be replaced every decade or so

But some hardware does last quite a long while. Fiber laid from 25 years ago is still pretty useful.