A Question for 9/11 Conspiracy Buffs

I can't pretend to have researched all this in detail, but at the behest of some apparently rational acquaintances of mine I have looked into it. And I have seen enough to know this much: if 9/11 was the result of a Bush administration plot, the scope of the enterprise was enormous. The resources involved, the people involved -- we are talking about a vast conspiracy organized by highly placed, hugely powerful, individuals.

The purpose of their operation is said to be to justify the invasion of Afghanistan and Iraq -- the long-term strategic goal being a permanent US military presence in the Middle East and Central Asia to secure oil supplies for the 21st century.

So here's my question: if these folks could arrange something as logistically complex as 9/11, couldn't they have arranged for us to "discover" some WMD in Iraq? That would have been child's play by comparison. If they had just done that little thing, their whole agenda would be on track today. Bush's numbers would have stayed up, support for the Iraq war would have held firm, and patriotic US citizens would be chomping at the bit for an attack on Iran.

How could conspirators powerful and far-sighted enough to organize 9/11 have failed to seed some remote desert bunkers with a few canisters of anthrax?

It doesn't make sense...