I wonder if the bunker buster was used. It has a somewhat indirect lineage to the ww2 grand slam designed by Barnes Wallis. Iran has massive earthquake risks. For reasons unassociated with nuclear bunkers they do a lot of research into (fibre, and other) strengthened cement construction. With obvious applications to their nuclear industry of course. Another unrelated point, a significant number of Iranian civil engin…
Can I say again how deeply silly this munition is? What's special about a GBU-57 isn't its explosive force. It's that the bomb casing is made out of special high-density ultra-heavy steel; it's deliberately just a super heavy bomb with a delayed fuse. It is literally like them dropping cartoon anvils out of the sky.
From what I've read, the idea is that they keep dropping bombs into the same bomb-hole that previous sorties left, each round of bombs drilling deeper into the structure.