Which will be totally useless if it's completely consumed by cryptocurrencies, thus only adding to further destruction of the climate.

That doesn't really help if crypto is also consuming the renewable energy it "helps" build-out.

The problem isn't that the relative proportion of renewable energy is too low, but that the consumption of non-renewable energy is too high. It doesn't matter if renewables make up 10% or 90% if that number doesn't mean a large reduction in the consumption of fossile fuels.