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?
That’s just not how business is done… Utilities have investors and boards, etc. Those people have diversified investment portfolios and long term financial plans. Their investments serve purposes and it is important that the underlying businesses play their role and not chase whatever fad is hot at the moment.
Basically, businesses don’t just change their business models. The shops that sold shovels to gold miners didn’t close down their thriving businesses to start digging in creeks.