The miners (as they try to have the biggest profit) are looking for the cheapest electricity available. So if the state does not influence the market through subsidies (or other interventions), miners are forced to use the green energy because it is much cheaper. In the free market, it is definitely less profitable to mine with dirty energy. As it is mentioned in the article, every entrepreneur have to produce more valuable outputs from less valuable inputs, thus if the dirty energy is not subsidized, its users pay more for electricity (in most cases).