This is a thought experiment and please feel free to correct me if my presumptions are wrong

Assuming an entity or a company decides create a sustainable mining operation. So he sets up wind farms, solar, water wheels etc to generate the electricity. But now that he has all that electricity, why not just sell it to the grid? I know that those that have solar panels can do that if the panels generated more electricity than the owner used.

So let's say that mining is more profitable than selling to the grid.

OK, then what stops the big utilities from using their electricity to mine as opposed to selling it to the consumer? The regulator authorities?