The amount of money for a given amount of energy spent mining you get is effectively Bitcoin price / difficulty.
If Bitcoin price goes up, then the return on energy gets greater. Therefore, it's worth it to spend more energy mining. Then difficulty rises and takes this incentive away, reaching a new equilibrium with more energy spent.
If Bitcoin price goes up, then the return on energy gets greater. Therefore, it's worth it to spend more energy mining. Then difficulty rises and takes this incentive away, reaching a new equilibrium with more energy spent.