cannabineer
Ursus marijanus
I can only do this by analogy with block C Harpoon, a largely similar missile. It consumes 780 lb of fuel per hour but has a flight time to max range of 12 minutes (120 mph max range at 600 mph) which requires 156 pounds of fuel. This is a bit more available energy than the 330-pound warhead of Neptune, but half that fuel will be gone. Being generous and imagining that Neptune has similar range but a less efficient sustainer engine, half its fuel remains so ~100 pounds. It would have to be a bullseye on the magazine for that burning fuel to make a difference. But hey, that could have happened! The proof of the pudding is in the eating, and Moskva certainly took it full in the face.Another thing is those Neptune missiles only traveled about a third of their maximum range, so there was lots of jet fuel left in the tanks. Reports said it was hit about 60 miles off the coast and if the missiles were launched inland a few miles, they would have got there fast at 600 MPH and would have had plenty of fuel to add to the mess.