If Mueller investigates Trump's financial activities in connection with the multiple investigations going on then according to Trump Mueller will be fired. That will be the red line that was crossed. The arrogant ignorance of a Trump cannot be more apparent then for him to think he has a say in any of it. HE is the one being investigated. He doesn't choose anything. He complies. QUIETLY. He doesn't moan and groan and kvetch and manipulate and plan and conspire and undermine and sabotage. He is impotent and is treated like any other citizen. He is not special. He is not above the law and he shows his utter disdain/contempt for the rule of law.