Tillerson couldn't stand his boss. (Remember the “he's a Moron“ comment that Tillerson refused to confirm or deny? (Truer words were never spoken, but I digress...) Early on, Tillerson said he'd only stay for a year. Trump wants people who will do as he says to do: mindless yes-men who will ignore their job description and simply do whatever he tells them to do. Vis a vie; Owner/ Obedient dog relationship.