Your argument would only make sense if we were using 100% renewables
now. We aren't.
How is crypto using cheap coal-powered energy a good thing?
Also China doesn't love crypto as much as you think. They've banned exchanges in China, banned ICOs, and they've already legislated against crypto once. Analysts predict they will regulate against it again, probably sooner rather than later.
Also electric is cheap in Iran, but it clearly wasn't "surplus" because the mining operators in Iran have been causing rolling blackouts, lol. Do you honestly think Iran has a massive surplus of energy? They are cheap to encourage businesses to operate there, but it seems miners are sucking them dry