Even setting 9/11 aside, Saudi Arabia publicly funds numerous madrasah in other countries which have a, shall we say, Wahhabi-aligned curriculum. Which then provide a steady stream of recruits for the likes of al-Qaida (or, these, days, ISIS). This might be indirect enough to evade responsibility, but the countries where such radicalization eventually translates to violence generally don't consider Saudis "mostly a good actor".