Creative Speculation

1) Many leading advocates of the "push the envelope" counterterrorism policies after 9/11 were some of the very same people who refused to explain the Saudi connection and their role in it.

2) Proponents of the protection money theory do not make a connection between the pre-9/11 conduct of US intelligence and the Saudi connection. Thus Sen. Graham talks of sharing failures instead of honing in on a more likely explanation--US intelligence was ordered to back off. I have speculated that there may have been look the other way deniability. Thus some high level officials could block al Qaeda investigations on a general basis so as not to make the Saudi royals look bad. After 9/11 these officials could pretend that they had no idea that something bad would happen when al Qaeda investigations were obstructed.

There are other theories. I would use the example of a branch chart. We don't have good enough information to complete the chart so we are left to speculate the correct progression of the branches.