Tower 7 was damaged by tons of steel and concrete falling from the larger towers. The initial FEMA estimates of damage to #7 underestimated the amount of damage. This is not surprising considering the circumstances, the early assessments from FEMA are always preliminary and are based on very cursory visual inspections.
The damage also started a fire. The fire was fed by a large pressurized fuel line used to run emergency generators. It burned without any attempts to extinguish the fire for 7 hours. Between the initial damage done by the debris and a raging fire that burned out of control for 7 hours, the steal trusses started to fail.
The weight loads started to shift from one support column to the next, as the trusses failed. . This was how the truss system was designed so that a failure in one truss would not cause a problem, but the designers never anticipated the extensive damage caused by such an intense fire combined with the initial damage. One support column had been severely damaged as a result of the initial damage. As multiple trusses failed, the support columns holding the surviving trusses became over loaded. Once the weight exceeded the maximum structural load on the columns the entire column, along with the trusses that it supported came down. This cascaded through out the structural framework on the building causing catastrophic failure. That resulted in the buildings collapse.
With even a small understanding of how a structural truss system works, that each piece depends on the integrity of the next, it is easy to see that major damage can eventually lead to a catastrophic event.
If you think about Occam's razor what do you think is the simpler explanation? A few tons of debris combined with a raging inferno can bring down a building or a massive government conspiracy requiring the complete cooperation of dozens of individuals without a leak resulted in the intentional destruction of the World Trade Center, the death of thousands of people, including the suicidal pilots of the commercial airliner that flew into the buildings.