You generally lie to get yourself out of trouble. Thinking that someone who just admitted to lying, admitted they were wrong to lie, apologized for lying, and generally took responsibility and said they deserved what they got must only be doing it as part of an even bigger lie seems to be getting into conspiracy theorist territory on the scale of Truthers, to me.
"Rig the Twin Towers to explode, sneaking around for months or years to do so. Then hijack four planes... we'll put them somewhere hidden, and scatter some debris that's NOT from them in the wreckage. We'll do all of this to start a really, really unpopular war. But make sure we do it all so incompetently that any kook on the internet can find us out."