As I understand it, Bitcoin mining rewards are now so low that it's unprofitable to use fossil fuels to mine -- you will pay more for the electricity than you receive through the reward. Hence a lot of people moving their miners to somewhere in the world with unused excess renewable (e.g. hydroelectric) power and setting up there.
For a "professional" miner, price swings are irrelevant. The same quantity of bitcoin is mined independently of the price. Bitcoins mined in March are worth the same of bitcoin mined today even if price is 10x now. And in March the same hardware mined more bitcoins than now.
Big miners are datacenter sized now, and such things are not built during a bull run.
It's true that miners are relocating to locations where energy can be purchased at lower prices.
It's not true that there are large reserves of unused, excess power that would otherwise go to waste if not for these miners putting it to use. Power companies everywhere are experts at sending energy around the interconnected power grid.
Miners running profitable operations have zero desire to establish expensive mining operations and only run them in narrow windows of excess energy capacity, such as peak wind and sun days.
The narrative that mining is relegated to purely unused, renewable energy capacity is an attempt to whitewash the massive power sink that is cryptocurrency mining.