There are two lines of questioning, one is character based when relevant during a scandal, the other more presidential are policy based.
Megyn Kelly went into lawyer mode to humiliate a witness in front of a jury on issues not relevant to his choices in terms of people he associates with or policies he chooses.
That he is unartful when he fires or scolds someone is a total BS detail that would only concern the civil servants working under him.
Kelly’s question might just as well have been “When did you stop beating your wife?”