The first attack on the Trade Center attempted using explosives in the belief that one tower would collapse on to the other.
It didn’t.
bin Laden had studied architecture and knew it was a steel building.
Heat is the enemy of steel, Not explosives. Heat is what bought down the buildings.
Not just that it was a steel building but that it was built without a central concrete core and instead relied on an external skeleton. Once that the external skeleton was compromised, the building was coming down.