Hmmmmm.... I thought the impact/blast blew the very fragile fireproofing of the steel support members. Then the burning jet fuel and bldg contents heated the exposed steel sufficiently that it couldn’t support all the floors above the fire. This seems pretty legitimate to me, what’s the problem with it anyone?
Regarding the fireproofing, recall that leftwing activists and attorneys stopped the use of asbestos containing insulation about halfway through construction. If you ask me, they’re to blame for the collapse.