Equal and opposite reaction, anon.
All of the mass of the towers can't move without something to push against (sideways). If the tower could no longer support ever how many thousands of tons above it against gravity, how could it also serve to push that same mass sideways?
Bolt-and-bracket =/= weld, anon.
Bolts concentrate stresses. Heating of joists and spars can affect the temper with subsequent cooling.
It is "possible" that explosives were planted to make sure the towers fell. But it is not really necessary to explain why the towers fell.
Buildings as large as the WTC are never demolished using explosives.
As dimensions increase linearly surface area increases by a squared rate, mass increases by a cubic rate. In order to move mass, you must have an equal and opposite reaction force. If the spars have already given way to the force of gravity, then how effective will they be at accelerating that same mass to one side or the other?
Controlled demolition is not just about keeping a much smaller building from having pieces of it fall sideways, but it is also about breaking up the building into manageable sections for recovery.
It's called "metallurgy."
Or "structural engineering."
The bolted joists/bracketing of the WTC on its upper levels was a cost-savings venture that ultimately weakened the overall structure and would be particularly concerning in regard to metal fatigue as the flexing of the structure in the wind would create a problem.
You have been given multiple keywords sufficient. I have no interest in those too content in their knowledge to seek more.
What most people do not seem to understand is the mass/surface area problem.
As dimensions increase, surface area increases by a squared ratio while mass increases by a cubic ratio. This is why large buildings can't simply be concrete slabs stacked ever higher and building design, itself, has to be completely re-thought.
The steel of the WTC losing even 10% of its rated strength from heating would be enough to create concerns.
But any time you heat and cool metals, you run into problems with the crystalline structure. Just ask any bladesmith.
If a section of steel within a beam is heated and then cooled, the temper of that section of steel can be altered. What was once a very hard yet flexible tooling wonder-steel can now be weaker than aluminum and have a nasty propency to shear as opposed to flex.
While this is unlikely the case in structural steel to see such a radical change in properties from re-tempering, one must also rember that the building was at the limits of its own design theorem. It was designed to support itself and had a buffer to deal with tragedy. The construction deviated from print by using bolts in the joists rather than welds, and it was quite possible that the building would not have survived what it was designed to withstand on paper. Although that was still the era where engineers liked to over-engineer.
How many steel buidings are 100 stories tall and have caught fire?
The belief that the towers needed the GDI Ion Cannon, the GDI Disruptor, or the GDI Commando to demo the WTC over the planes flying into them is simply a distraction seeded from the outset.
People immediately turned away from researching the flights and the suspects (and their ties) and instead ran off into the woods with no-plane theories and the like.
Some of us were a part of those arguments way back then.