Why isn't it credible that the purpose of the war in Iraq was to cover up that Bush was warned about 911 and did nothing?

We know that Bush knew that the New Orleans levees would breach, and we know that he did nothing with that information, when he could have saved at least lives if not property if he would have contacted Louisiana officials. So, in another life-threatening circumstance, Bush did nothing. That isn't benign neglect; it's CRIMINALneglect.

Knowing about 911 and doing nothing would have been treasonous and impeachable.

I'd quibble with the thought that it was the sole purpose of the Iraq invasion, though. The interests of PNAC and the oilboyz also played a part.