The conceit here is that the WTC attacks were part of some conspiracy designed to get us into war in the middle east, presumably by the Bush Administration. Supposedly, the buildings were rigged with explosives so that if the airplane attacks weren't enough to bring them down, they could be destroyed using standard building demolition techniques (timed explosions, etc). The evidence for this is the orderly and symmetric ways in which the buildings collapsed, and supposed evidence of chemical traces of demolition explosives, such as Primacord and Thermite, and now, alleged precise cutting of structural supports as shown in the images (which Lee very effectively demonstrated to be gargonzola). The idea is that after the (faked) airplane attacks, these carefully placed explosives (which had been being installed for weeks before the highjacking) were set off in a coordinated fashion.

My only question is, why bother? Even if the basic premise of Bushian trachery was correct, once that first plane hit the first tower war of some kind was already assured. Hell, even I was ready to enlist.