Reading between the lines of the Zac article...twelve months ago CM started assembling a staff. He knew he needed recruiters and he needed X and O guys. Matt A, an SJU grad who knew Chris, was an obvious choice for recruiting. St Jean, more of an unknown, might have been brought in due to CM's relationship with his father, or maybe he interviewed really well from an X and O perspective. CM looked at Slice as one who were be given preference to do both, why else bring him in?
As time went by, St Jean earned more of CM's trust as an X and O; Matt earned more of CM's trust as a recruiter. As an older guy, Slice said to himself, "what am I doing here playing second fiddle in recruiting and strategy"? Slice is taking his bruised ego down the road, possibly to more familiar pastures. Much like the veteran ballplayer being replaced by the younger prospect.
I always preferred a more experienced X and O guy. Some one with in game coaching experience. Dunlap would be perfect, Tim Welsh, Pete Gillen have been mentioned. I also threw Mark Jackson out there. Just give us someone who can work strategy, especially teach defense, and has college coaching experience.