He didn't have to stay.
Remember, he has head coaching experience. (Yes, I know it was with the Cleveland Browns. And yes, I know he went 10-22.)
But he has head coaching experience that could easily be translated into another defensive coordinator elsewhere.
Of course, I'm talking about Packers defensive coordinator Mike Pettine. He was hired in 2018. Little did he know that things would quickly unravel and his head coach would be fired after 12 games.
He stayed on for the rest of the season and then the Packers hired a guy in Matt LaFLeur that had zero head coaching experience.