It would fit into tRump's narcissism.
After all, McMaster is competent, knowledgeable, and appears to truly support the national interest.
All things that tRump is deficient in. Things that cast tRump in a backup role when it comes to national security. A role his fragile ego can't tolerate.
Plus, McMaster brings fabulous qualifications to his position.
tRump? I report, you decide.