Actually Israel is known to use a double tap bombing method that waits until reporters and aid shows up to the original site and then they strike it again to take out additional people to make it harder to respond to the next attack.
Also this was a cluster munition bomb ment to shoot shrapnel out, the goal is to just hit solid ground to make it explode sideways, they just happened to double tap exactly the same spot and there was a cavity under the road.