The hijackers were al-Qaeda terrorists. Their 9-11 leader was from Egypt and the attack itself was "orchestrated by al Qaeda leader Osama bin Laden" - now deceased. And they also came from from Lebanon and United Arab Emirates as well. 

 Lacking bin Laden, now there is likely very little reason to be so concerned with Saudi Arabia as a terrorist hub.

So your point is this?  Effectively remove all terrorist leaders to have the same outcome as Saudi Arabia?  Okay! 

http://www.cnn.com/2013/07/27/us/september-11th-hijackers-fast-facts/index.html