Let's not be naive here
Whether it is being reported as such or not, the plain fact is that the top political appointee, in other words the Secretary, didn't envision tolerating the classy, sèlf-effacing, and always with high-fidelity technically, manner in which the estimable Mr. Nolen conducted the office of Administrator (Acting). With election season looming, the tolerance(s) for the Sec'y DoT getting upstaged - even by such a dedicated public servant - had to be declared "over."
Call me cynical, but . . . . . .