As has been noted and answered many times of the years, the smaller buildings took major damage when the bigger buildings came down...
Just because you don't believe it, or you don't understand the physics at work, doesn't change anything.
In fact, it's a tad arrogant to think that, "If I don't understand it, then it must be something bigger or more sinister"... It implies that you are so smart, that anything that you can't compute, has to have another reason.
Kind of like how humans ascribe anything we can't answer, to the supernatural... Hence why we have religion...
How did the universe get here?
Must be a magical sky wizard, we will call him god, that just clapped his hands and created all this on the spot! Yeah, that makes sense...
How many buildings have collapsed in on themselves from office fires?