“There’s no reason to fire him. I asked him, ‘Do you have any reason to [fire] Mr. Mueller. He said he has zero reason to believe anything is being done wrong with the Mueller investigation,” Graham said, recounting the conversation.
I can think of a reason to fire him: money. He - and his staff - is being paid big bucks to look for a unicorn. The government can use that moola to pay down the debt - or most anything else - more usefully that that.