Why blame only one President for 9/11?

The Left Wing and Right Wing have been trying to shift blame for 9/11 on either Clinton or Bush ever since it happened. C'mon! How can only one of these guys be to blame? Terrorist groups had been growing under President Clinton's watch and were ready to do some major damage at the end of his Presidency. And what did Bush do in his first 7 months in office to fight terrorism? What did he have to say about terrorism when he was running for President in 2000? If you only blame one guy then you're a partisan hack or you're just ignorant.