Why Do Presidents Tend to Distrust Career Diplomats

Why do presidents tend to distrust career diplomats?

A) Presidents cannot be certain of the diplomat's political party affiliation.
B) Diplomats lack sufficient training and expertise in many instances.
C) Presidents generally do not know the language and culture that the diplomats are meant to serve.
D) Presidents are personally responsible for actions,so they prefer to send special envoys they trust.
E) Presidents are intimidated by the education and training of professional diplomats.