I suppose system could just be another way of saying culture/philosophy/way of doing things.
What someone does over the course of time.
He did it at Utah and Florida as OC under Meyer to great success. He did it on his own to moderate success at UF post Meyer, but he was replacing a GOAT and incredible level of achievement so not sustaining that got him. A victim of his own success as OC/right hand man.
But then he did it again at State to great degree of success for that program.
His ability to evaluate, recruit, then develop them to produce at high level. Specifically, passing game skill talent and QB.