It's more like you offering to invest $1bn in Fred's company in return for a promise to spend $1bn for sink fixing services. You could question if there is a demand or $1bn of sink fixing in the same way that you could wonder about the demand for $100bn of AI slop.
Investing is just an equivalent value exchange. My point is that while you could say in my example that money just moved around in a circle, it turns out that money moving around in a circle is actually fine.
I agree money in a circle is fine. But in your example there is a straightforward situation of an end customer paying money for a service, eg. getting a sink fixed. The worry with the data centers is will there be enough end customers willing to pay what the data centers cost.