It’s also undoubtedly true that the act of hitting the ground with stories of concrete and steel above melted some of the steel from friction.
I work at an engineering company (trained as a structural engineer but specialize in something else).
Back in 2001, one of our top structural engineers said he had figured it out. He knew exactly why the twin towers had fallen, and he could explain it to us.
I was interested - yes, please tell me, why did the buildings fall down - from a structural engineering perspective. What secrets do you have? What do you know, that the rest of us don’t?
He gave me a serious look, and I prepared to be enlightened. Out came his wise words:
“They flew f@#$%ing airplanes into them!”
I always thought that was the most succinct explanation I have ever heard on why they went down.