When you talk about this.. have you for once stopped to think that the WTC was hit by object that weights between 60000-114000kg:s depenting how it is
loaded.
And this object moved 300-800km/h.. (max being 500mp/h)
And the 'object' (missile, plane..) exploded as it (they) were carrying much fuel.
Structures hardly ever collapse 'at first impact'.
But usually 'shortly after' as the structure 'wears itself out'.. ('fatique') as the 'weakened' structure cant stand the weight.. but it takes
a short while before it collapses. (due 'fatique'.)
I hope that you can understand what im saying..
(my point simple as possible: metal 'cracks' after certain timelimit if 'somekind of force or energy' is 'affecting' it.)