The exterior walls were mostly glass. That is the style of modern skyscrapers. They were not significantly concrete. The exterior wall had steel columns...among all the others in the core, which were holding up all that weight. There is utterly no mystery about this and I don't understand why I have to explain this to you like you are a child. Did I not give you the reference to the B-25 collision with the Empire State Building?---which was a much less serious event.

As for the building "still standing," I didn't catch that except on second reading. What possibly can that prove? We normally expect (for example) that automotive head-on collisions are terrible affairs with loss of life and mangled vehicles. But I was in one where I was essentially unhurt and my car had mainly cosmetic damage. So also, the other party. You can't draw rules from discrete events. There was nothing else like the Twin Towers event so far as I am aware. And the "still standing" building was only about 20-25 stories. The photo shows the fire department working to abate the fire. No possibility of that at the height of the Twin Towers collision. You are not making a logical comparison. The majority of professional opinion was that the collapse was understandable. As an engineer, I find it understandable. What more do you want? You don't seem to be approaching this as an engineer, or as one familiar with structures.

WTC7 also collapsed from columnar failure from an internal fire (innards first and walls last).

The exterior walls were mostly glass. That is the style of modern skyscrapers. They were not significantly concrete. There were steel columns...among all the others in the core, which were holding up all that weight. There is utterly no mystery about this and I don't understand why I have to explain this to you like you are a child. Did I not give you the reference to the B-25 collision with the Empire State Building?