It was just a guess I figured I'd throw out there..
I know there was a discussion back and forth about the pronounciation of Vitali Klitschko's first name during advertisements when he fought in Germany. It had something to do with the way Germans had a difficult time pronouncing his name, so they changed the pronounciation of his name for that fight. American boxing then thought the German pronounciation was correct and began saying his name incorrectly - finally he told everyone the correct way to say Vitali.
The discussion was between saying "VIT-a-li" or "vi-TAL-i" - I don't know the reasoning for the German pronounciation.. I don't speak German.
Regarding Moskva - perhaps something similar happened in the pronounciation from various cultures to evolve it to Moss-ko in the USA.