Once again, going back to the NIST interim WTC 7 report, the lower floors were cantilevered over a ConEd substation (see pp. 9-11).Adding to pt 6, was WTC 7 not an air-rights building and therefore the major structural support on the sixth floor consisted of cantilevered support beams?
A failure of a column there would have affected a very large floor area and rapidly distributed loads, leading to what Christopher7 calls a "previously unknown global collapse," and what NIST calls a "classic progressive collapse." (ibid, pg. 6)