The issue is clearly a tragedy of the commons - the cost (higher air pollution/higher energy costs) is socialized, while the profits are centralized. So the maximization function is cheap >>> anything else. Why wouldn't we expect more and larger coal plants versus research into fusion reactors?
Unsubsidized renewables are already the cheapest new source of energy generation. [0] Even if miners wouldn't be doing direct renewable research themselves, their capital investments into renewables in the name of competition and cost-savings would incentivize more efficient technologies.
In this case the immediate marginal profits from mining are centralized, and the larger benefits of more advanced renewable energy are socialized.
Plus - do you believe that the price of Bitcoin will rise forever? If it did, wouldn't that mean to you that it might be doing something important, to constantly have growth and demand for 100 years? Cuz if I thought so then I'd want to preserve it, not throw it away. Sounds important.
[0] https://www.forbes.com/sites/jamesellsmoor/2019/06/15/renewa...
Even if Bitcoin isn't intended to be "growing forever", the ecosystem can and will.
Shameless hijacking here: at what point will the heat consumption/release rate be so great that the Earth becomes unable to support life? I've seen some back of the napkin calculations that estimate a couple hundred years, at our current acceleration.