If you investigate just about any "elite" unit (or army for that matter)you mostly find a superior command structure that creates an overperforming unit by that alone; if the unit also benefits from selection of the lower elements that further boosts the combat differential (whilst weakening the standard units of course).
Unitl they took the TRADOC off general access, you could see this in the Field Manuals for US infantry, where the Ranger unit had a superior command structure to all other infantry units - Rangers were elite by the definition of their command structure.
A lot of this has been only recently been understood in the civilian world; look for books on "Organisational Behaviour" in Management studies; there are sections on command structures (they call them management structures). The principles involved are based on the human pysche and there is no great difference between soldiers and office workers in terms of the main behaviour triggers, and how groups interact and react to management styles.
Its a deep topic that hardly anyone has yet barely scratched the surface.
PS Can you guess its my pet topic?