The WTC was fairly unique in its design in that it structurally was closer to box tubing than a pole or truss with cantilevered floors.
Even had a 727 crashed into the Florida building it probably wouldn't fall. The WTC collapse was IMHO well planned ahead of time and probably chosen in part because of those features as well as its reputation as a landmark.
The best way to insure more terrorist attempts is to create kneejerk regulations which alter our culture in response to each of these little episodes. Essentially we're dealing with little spoiled kids who never learned that they won't get what they want by acting up. If our society hasn't matured to the point to realize that those who are so immature should not be given any quarter, then we probably deserve to not remain in any controllable power.
The actions of terrorists don't warrant abandonment of Constitutional rights for the public, they warrant the curtailment of rights of the terrorist.
It had to do with the full load of jet fuel, which would melt girders of any style of construction.
Asbestos was one thing which could have delayed them coming down, but unless that fire was extinguished or minimized, those buildings were coming down.