“Who hires/fires Kellogg? “
Trump did.
“President Donald Trump put Kellogg in charge of the presidential transition agency action team for defense. He was named a foreign policy advisor to then-presidential candidate Trump in March 2016....On December 15, 2016, it was announced that Kellogg would be appointed Chief of Staff and Executive Secretary of the United States National Security Council by President-elect Donald Trump.”
“2) Do you think McMaster had zero influence on Kellog?”
Not zero. Just close to it. Kellogg is a Lt General, the same as McMaster. He was also interim NSA between Flynn and McMaster. Hiring and firing NSC staff is Kellogg’s bailiwick and there’s no evidence that he is in the habit of turning over his prerogatives to someone else.
The only “evidence” of McMaster’s nefarious influence over personnel are the usual rumors circulated around here by people who wouldn’t know Keith Kellogg from a box of cornflakes.