cabinet is slightly different than personal staff.
Rex Tillerson gave up a third of his net worth, and any chance to make a difference in his net worth, in order to be a check on trump as Secretary of State for four to eight years. This was the capstone of his career, what his life would be known for. When he wrote is autobiography, it would be one chapter before his tenure, 20 chapters of his tenure, and a page or two for the years afterwards.
Tillerson lasted a year, and is reportedly saying the world would have been better had he never existed.
Jim Mattis was trying to recover his career from the Theranos scandal. He only had a few years to do so, and could not afford a bigger scandal, or his career would be sunk. He risked everything on being trumps Secretary of Defense. He desperately needed trump to be sane for four to eight years. He was promised by Tillerson that trump had things under control.
Mattis lasted for two years. He cannot get a job teaching at community college now. The nickname "warrior monk" is exclusively spoken now as a joke.
Mark Asper came in to replace Mattis as Secretary of State. trump threw the position open to whoever would take it. No one wanted it, until Asper stood up. Unlikely the previous two, Asper knew he was sacrificing it all for just holding the line against trump.
Asper lasted two years, and resigned after he realized to his relief that trump would not be reelected. He realizes that he will never be considered a hero, but almost certainly feels like a hero for keeping trump from destroying everything.
David Norquist was the brother of Grover Norquist, who in turn was a minor political operative. Not much more to say about Norquist, other than he was forced to be acting Secretary of Defense when no one else in America would take the position. He kept stressing that he was only acting as Secretary of Defense, and would not be officially being the Secretary of Defense.
Norquist was out of office with trump in two and a half months. He is still scared he will be convicted of treason for even being an acting Secretary of Defense.