You're correct actually, I was thinking of the GBU-57 MOP, not the GBU-43 MOAB.
You're correct actually, I was thinking of the [GBU-57 MOP](https://en.m.wikipedia.org/wiki/Massive_Ordnance_Penetrator), not the [GBU-43 MOAB](https://en.m.wikipedia.org/wiki/GBU-43/B_Massive_Ordnance_Air_Blast).
MOAB stands for "Massive Ordnance Air Blast", so I'm pretty sure it also explodes in-air.
Russia's bomb was developed later, so I absolutely believe it can be a more powerful weapon... but that is textbook US/Russia one-upmanship that we've had going for ages.
It's kinda comforting to see them back in the game, actually. Probably because the MOAB (and similar devices) only work well in areas that you have an entrenched enemy and absolute air superiority; this is type of weapon has little practical application fighting the West.