Caporegime
In the NIST report iirc it mentions the internal structures had already started to collapse before the exterior walls did, due to the extra strength/stiffness of the exterior walls. You can see this with the structure on the top and in the middle of the roof start to sag and fall down before the exterior walls move. It's then not exactly a leap of faith to see how this would cause the building to fall down/inwards rather than topple over - (IANAEngineer)
Your explanation is bob on. IAAEngineer