As I said in a sibling comment, the important metric is price, because of gas fees and mining profit incentives. Price goes up, more miners start up, difficulty increases, more carbon burned, Earth dead.

Also I/O here means adding a block, which is proc-bound, which roasts the planet.

Finally, video games have entertainment utility. Cryptocurrencies have no non-crime utility. It's not useful to compare the energy use of things that have utility to things that don't.