When they want to fire you, they can find a number of reasons, including too many bathroom breaks.
The reason(s) he is being fired for were the kind you’re looking for when you want to fire someone. They looked for something as they were told to start looking.
I hope he fights this, because it is a political stunt, orchestrated by Uncle Wally. By now, we know how he works. Firing Tillerson that way is just another piece of knowledge for us all. And he did it that way because Tillerson called him a “fkng moron” last summer.
But, patience. He who laughs last, has the best laugh.