SAF had some footballing substance to it also, it was still about the football. Mourinho lately has been only about pep talks to players, getting under skins of other managers (like that is important) and intimidation of referees. That has worked fine for years because he had this aura of invincibility, the players believed him. Now he has messed up at Real and Chelsea, and become more of a clown and less of a manager/coach.
United will not only risk youth players and loosing fans with boring football, but also risk signing last decade's best manager. There's no guarantee he's anywhere near the best managers in the current decade. If you really want a cnut for a manager, at least go for a young and promising cnut.