As the popularity and price of Bitcoin and other cryptocurrencies increases, more and more miners want to mine cryptocurrency. The more people mine cryptocurrency, the more difficult it is to get it and the higher is the cost of Bitcoin and other cryptocurrencies mining.
As a result, those miners who have a lower electricity cost win, since they have more advantages. Usually, those miners where electricity is cheaper get a large profit. The use of renewable energy sources makes it possible to significantly reduce the cost of mining and mine more cryptocurrency to have more profit.