Suppose those could have been before the China exodus, but I thought they'd simply moved to other, cheaper places anyway where hydro made that possible... but I am reading now that I could have been mistaken that majority of Central Asia energy came from hydro.
It's not the majority but even though it is indeed high there is another drawback, although it's large in percentage it lacks in total capacity.
So you have Tajikistan producing its electricity from hydro, but that only amounts to 16TWh, UZ has 14TWh, TM has 4 TWh, KG 11, and KZ 8 TWh, this leaves little to spare for miners, and no real expansion has happened, not one that would match the growth in population anyway.
For comparison, just the state of Washinton has 89.5 TWh production annually, or if we count all electricity from all sources, Texas has more than central Asia combined, twice! Even if we assume all the network would be powered by the most efficient machines, all that energy won't be able to feed even half of it