Ok WTC was taken down by a crack demolition squad.
The insurance company approved because the saving the building on 9/11 would have made it's future demolition unbelievably expensive with all the other buildings around and other surrounding human interaction. So a decision was made wtc 7 would be best dropped on the day.
Why deny it? Because the yanks love to sue. Any knowledge of a deliberate drop like that in a built up area would of caused damage to surrounding buildings and opened up all sorts of anger at a time where families had their deceased loved ones in the erea.
Just an example of one potential logical conclusion rather than the x-file stuff.