Nepotism and, consciously or not, weaponizing his own patheticness for his survival. He was a brown nosing faggot whose distinct incompetence made him very appealing to management who liked getting their asses licked by an incompetent who could never threaten their own position.
Of course anyone competent could see how badly this would go over as he fell down the stairs and ended up in the attic over time or more simply "Gamekids Trevor???"