It's easy in 20/20 to look back and say he should have known, but I wouldn't personally fault him for it
I don't know enough details of what was known to pass judgement because of security clearance to know it. Still, there was enough known that they should have been on high alert. Obama had his team working from the night of his election forward (Office of the President Elect). I don't give Bush a pass.
Obamie wasn't mired in laws shits so he was able to set up his team before he was sworn in.
How do you know we weren't on high alert?
There was no specific threats, it was general chatter.
I'm just saying I don't hold Bush personally responsible for 911 but there plenty of other thing that really are his fault to be held personally responsible for.