"This does not apply in this case. These terrorist, and yes I refer to Iran as a terrorist country, do not have a specific concern with the endgame. Their survival is not a necessary component of victory, only the destruction of their enemies."
To them Israel is a proxy for the real enemy - us. They cannot "destroy" us - no matter how bad a few nukes would be. The result WOULD BE our damage but their annihilation, and they know it. We would survive, we would eliminate them and there would be a world that would not have an Iran and its "end game" afterwards.
They are fully aware of the wholesale escalation that would commence if they made Israel a glowing hole.
The retaliation, the global economic collapse. Other players becomming involved. Global chaos. The destruction of our way of life.
Trust me, they would use it.