2. It explodes.
And it takes 8 months to make that work?
The Iranians are using a sophisticated form of concrete called UHPC(Ultra High-Performance Concrete), Also called "Smart Concrete."
When the Air Force first received the MOP in 2011, it was unknown if these bombs would be able to penetrate several feet of UHPC.
So the bombs had to back sent back and upgraded.
At 30,000 lbs it could be filled with inert, non-explosive concrete and still make a hell of mess.