Now as for the videos... I tried to at least give them a review this morning but between the British accent and the heavy Russian accent, I couldn't understand quickly enough to keep any sort of interest.
I would not totally throw out any theory that includes the possibility of additional demolition devices used during this attack. If there were such devices, who put them there, why they were put there, when they were put there, etc. are all questions that may never be answered. Let alone proved or not.