Why and how did world trade centre building 7 come down in its own footprint?

Answer 1

It did rather exceed it's footprint, but the reasons it didn't "fall over" are as follows;

1. The structural failure was towards the top, so the bottom was fine and thus all stayed upright until the vertical shock loads of the falling floors above caused failure, which was progressive and local.

2. The walls were 'tied in' by the floors, so did not individually 'fall out', except for the small components after failure. There would certainly also have been a central 'core', with stairs, lift shafts etc, which would have failed last, so each floor would be likely to have 'slid' down around the core on impact of the floors above, before the core itself failed.

2.