I wonder if those that resigned are Carter and/or Clinton appointees.
Whoa. You seem to need an education. Service secretaries are political appointees in this case Wynne is by Bush and serves at his pleasure or until the administration is over.
Service Chiefs are selected by POTUS whenever there is a “need” (term expires, retirement, death, resignation)
Carter was POTUS 30 years ago and the Clinton Presidential era ended 8 years ago. Neither one was involved.