The suspicion is that Priti Patel has little or no leadership skills, or finesse. Those with experience of working in the public sector will have observed the type: clever, highly driven, superb networkers. But as to the detailed aspect of their roles, usually lacking. So, rather than getting on top of her brief, Patel goes straight to machinations and undermining her inferiors. Some argue that an intransigent UK deep-state requires such measures to jolly them along, but I fear Sir Humphrey has seen it all before.
One can't expect too much from a politico; their skill set is more in self-promotion than managing people, or dealing with Sir Humphrey. Already however we have The Guardian slyly leaking that Sir Humphrey has an issue with 'Strong Women'. Is this a new protected class, about whom there can be no criticism? Strong Women are ten-a-penny, ask any young man; competent leaders more rare.