10. Well, no. An exposed cover-up is not a mystery.
The cover-up is there for all to see. Since evidence of a cover-up is also evidence of concealment of a crime, the penalties for such behavior are enormous--like, life in prison enormous.
So there is no mystery about this: whatever complicity the Bush Admin had in protecting Abramoff and his financial relationship with the 9/11 terrorists, it was a criminal relationship so devastating that the cover-up was worth the risk.
It doesn't matter what they did. Making sure nobody knows what they did in the middle of a crime in which a thousand innocent people died, and an aftermath which killed a million people, is a crime worthy of execution all by itself.