Also, any such mining rig could have reasonably been a data center or scientific supercomputer instead.
And the argument about energy isn't straightforward either. Most bitcoin mining sites are set up where there is an excess of energy - when I had miners a while ago, I used a place in Newfoundland, Canada to host them, because of the local hydro dam. The water falls through the sluices or goes via the generators, it's just based on demand.
The chips are made with recent-ish nodes, so the silicon/fab capacity could theoretically be used to make CPUs.
edit: looks like at least one bitcoin ASIC maker is using TSMC 7nm, the same process used to make AMD CPUs.
[1] https://blog.bitmain.com/en/bitmain-announces-next-generatio...
Which would have been used for what? Supercomputer centers are having difficulty selling their cpu cycles. A data center for what? Figuring out how to better serve ads?