Without having any architectural knowledge, I'm going ask this question:
Why did ANY of the buildings collapse the way they did? Were they not designed with various forms of "stress" to the entire structure, etc. taken into consideration? Is it possible that brilliant "mankind the engineer", can't be sure how such structures might react when an unforseen, unexpected force threatens them?
Just asking... Give me the cliff notes.
Buy hey, I'm kind of a skeptic on certain issues. I don't believe that aliens from galaxies far away are necessarily going to visit earth in little spaceships made in shapes that the physical laws of our planet support, to date anyway.....or that they will be made out of steel!!!!
"...Without having any structural engineering knowledge..."