It is more important they are loyal to the Constitution and laws of the land. Not a man.
(not saying they are loyal to either, but way too much is being made out of loyalty to a specific individual).
The President needs to know that his policies are being executed and that the policies of those he picks to act on his behalf (like the Secretary of The Interior) are being executed as well.
That 30% could very well be in positions to undermine the rollback of Obama and even Clinton era land grabs and efforts to block energy exploration.
Why take the chance...give them a pink slip and let them try to catch on again during the next Democrat Presidency.