The kinetics matter here. The B2 flies much higher than the C-130 which would aid the GBU-57 MOP (almost certainly used here) in it's ability to penetrate to maximum depth. 80% of the 15 ton weight of that bomb is just heavy metal to give it maximum energy as it borrows into the ground.
Also, each B2 can carry 2 MOPs making it a better platform than a C-130, and that isn't even taking the stealth of the platform into account
Don't think the C-130s can fly high enough with a single 30,000lb bomb. The graphic at bbc site show it would be dropped from about 12km (~40,000 ft) in order to gain the speed needed to drive it some 60m underground.
The MOP isn't particularly 'advanced', it's basically refined version of the Korean-vintage Tarzon guided earthquake bombs. It's just too heavy for most military aircraft to carry.
The IDF has the F-15I which has a centerline hard point rated for 5,000lb load. That's immense for a fighter but a magnitude too low for the MOP.
There are a variety of smaller US penetrating bombs that the F-15 can handle, but they don't have the mass and structure to penetrate as deeply.
According to Israel they fly freely in West/central Iran and use all the plains including F15/16. Initially they relied on the F-35's stealth but as of last week they claim air superiority.
You are correct but although the B52 can technically carry the GBU-57 MOP, but it was only done that way during the initial testing of the weapon. The B2 is the only aircraft the USAF actually uses for that munition in combat scenarios.
Also the B2 is better suited for extreme endurance missions like this where the plane is in flight for >36 hours. It has a toilet, microwave and a cot for the pilots to use during the more mundane parts of the mission.
