2 things.

The House of Saud is amazingly rich and are Wahabists.

Al Qaeda hates the House of Saud.
One more thing. Bin Laden is a prince of the house of Saudi. Its more like a family squabal.

They are growing up in an enviroment of propogana and hate. Until we fix what is making these terrorist, then there will continue being terrorist.
And that enviroment of propogana and hate is radical Islam. How do you suggest we fix it?