I was involved in arson investigation and fire fighting in my younger days, and am now a professional engineer. Both of these schools of thought teach the same principle of high rise building failure during fires. That is thermal expansion of the steel. A long steel beam or column exposed to intense heat can grow many feet in length, resulting in column buckling or shearing of the fastening system.
I saw a building that had an accidental rocket motor burn take place in it. The building bulged out almost in the shape of a foot ball from the expanding gas. The building did not collapse but had to be torn down because warpage in the long steel beams made it structurally unsound.
Same thing happenes in high rise buildings with a different twist (intended pun). The concrete and steel interface adhesion will be destroyed both by steel warping and concrete spalling. The heat can travel through the beams to parts untouched by the fire and experience failures there.
Does anyone remember the collapse about fifteen years ago of an building under construction in Bridgeport CT? From what I remember, the top floor fell onto the one below it, causing a chain reaction.