The way the bomb was created and the way it was dropped.
The chemicals inside of it would create a chain reaction that creates a huge, nuclear explosion. I don't know the specifics of what was inside the bombs but it had a lot to do with nuclear energy.
And the way it fell/detonated.
Instead of letting he bomb detonate by contact with the ground. It exploded like 20 feet or something in the air. Hitting the ground would create an explosion that goes up, but detonating in the air means it goes everywhere.
I will attache a file so you can see what I mean.
Hope this helps.
