Maybe because Bitcoin mining is rapidly moving away from dirty coal-fired electricity generation in China, and toward clean and renewable energy sources. We're not there yet, but there's been astounding progress just in the last 12 months.

Or maybe because Bitcoin mining helps solve the intermittancy problem of renewable sources such as wind. Today there's a lot of supply at the times there's low demand, so it doesn't make economic sense to invest in enough wind power to make a difference when demand spikes. Intermittant Bitcoin mining provides a market for the surplus, then goes dark during demand spikes to match supply with demand.

Or maybe because the current monetary and financial system is so fantastically corrupt and broken that it's worth spending a fraction of one percent of the world's energy on an alternative.

Or maybe people use energy for all kinds of things that I think are stupid and wasteful, but I can't tell others how to invest their own resources.