A common reverse-engineered motive is that most of the paper evidence against Enron (including their dealings with the Taliban) were destroyed by the collapse.
Shredder. This thing could clean up library of congress in a weekend. And it can be done conveniently by one single person over a few nights inside a broom closet.
You know, as to not attract one billion eyes and 50,000 cameras to the process. A common requirement when trying to hide something.
And now, for something completely different:
Let's assume this was a conspiracy. You win. Now what?
Government falls? Ok. Since it was republican government it's replaced by democrats. With no opposition, unless you count independents.
The one-armed man is convicted, hanged, etc... - Well, it happened with Bin Laden, people partied, then had to go to bed since they had work in the morning.
US falls apart? This would go under "incompetence vs. malice". I mean, let's blow things up so that we weaken our global position cannot be a good plan.
People take control. Read youtube comments. Do you really want populace to be in control.
Key conspiracy investigators take control. These are people who have been studying 4 frames of JFK killing for 30 years. In what way would they be qualified for anything?
"Well, there goes our past time. But look, Jersey Shore is on" - probably the best outcome of all.