Yeah, someone definitely planted the charges in the lower portion of the building before the attack, along with the diagonal cabling from low columns up to higher columns. Oh, and don't forget the smaller charges to weaken key column and beam sections to help once the big mechanism is initiated.
The towers were 225 feet square, if I recall. You think that gravity acting downwards can tip a block of the top of the tower (which is not actually a solid rigid block) over sideways to spill onto a different lot? Do you realize the amount of force exerted on the outward line of columns if they were actually acting as a fulcrum for that?
Those towers had clear "lease spans" out from the core to the perimeter "tube" of closely-spaced columns. Lose a few floors of framing, and the exterior columns lose their out-of-plane bracing. Couple that with the altered load path due to severed columns creating an increase in load in the un-severed columns, along with potential softening of the steel due to heat from the fire, and there is the collapse mechanism. Initially ductile, possibly inelastic buckling local to the impact. Once the mass started moving down, there is a continuing cycle of floors getting overloaded due to debris impact / pancaking, resulting in failure of floor framing and the loss of the floor diaphragm removing bracing for those next columns below.
If the planes hit higher, the whole building may not come down. The second plane with the banked impact took out more levels of structure, which led to that tower collapsing first.
Conspiracy is bullshit