Call me a cynic, but I think that the reason that so many Trump administration cabinet member have chosen to resign is that they don’t want to be on the record making a decision about removing Donald Trump under the provisions of the 25th Amendment of the Constitution.
They think that participating in that would be disastrous for their future careers.
I know that you are probably thinking, “Future careers, surely you jest,” but let me show you Richard M. Nixon’s “last” press conference, which he gave in 1962:
Much like a bad penny, these folks will be back.