If the btc has greater value than the outputs from the renewables, then the market is "voting" on what is actually the most valuable thing to that society.

I know it's tempting to argue along the lines of "What could be more important than the environment?" and that is a good question, but that is a shift in societal values question, not an economic one. Economics simply helps one optimize the outcomes towards a values set.

If the computation had utility then it would be predictable.

Think of calculating digits of Pi. You can calculate the digits ahead of time and stockpile them, you can use your stockpile to do a 51% attack.