I'm something of a Crusades buff ... I'd say that Saladin did seek to legitimize his rule partially on a religious basis through the expulsion of the Crusaders, but that part is greatly emphasized largely by Christian and Western chroniclers. Just as or more important in domestic Muslim eyes at the time was his final coup de grace to the Ismaili Shia Fatimid caliphate in Egypt, returning those lands to Sunni rule.