There is no such thing as cheap energy. There is energy impoverishment for billions of people around the globe and ever watt used for one thing is a watt that can't be used for another. The supposed "cheap" energy being used to mine BTC is energy that can not be used to reclaim degraded landscapes, build decent schools for disadvantaged kids, transport food to market, do the accounting on local, national, and global supply chains, build solar or wind collectors, create smart grids to distribute the collected energy, and dozens of other crucial activities. There's no guarantee that the energy wasted on BTC will instead fill one of these necessities, there IS a guarantee that every watt wasted on BTC will NOT do so.