Why exactly did Iran use cluster bombs on Israel. It all comes down to overwhelming the defense systems.
Israel has the Arrow missile system, which is fantastic at targeting a single, large warhead. Iran knew this, so they adapted by firing a cluster weapon.When this weapon separates in the air, it releases a wide spread of smaller bomblets.
This completely overwhelms high-altitude anti-ballistic missiles, making it incredibly difficult to shoot them all down.
Because of the heavy moral implications, like leaving behind unexploded bombs, over a hundred countries have banned these weapons.
Interestingly enough, the US never banned them.
The American version can be fired straight from a One 55 mm howitzer. As the bomblet falls, the impact forces the pin to detonate, instantly triggering a shaped charge. This Can Penetrate Fortified buildings and Bunkers