Huh? The Bolshoi is not some regional company from nowhere. It has a huge international fanbase from their lucrative tours, livestreams, and their stars guesting all over the world. Many of these international audiences would surely be offended by the blackface.
Also it's a fallacy that Russians have few people of African descent. It's ironic that this particular argument is still used in the week a movie about Alexander Pushkin, a Russian writer with African heritage.
If the Bolshoi has NO dancers from different ethnicities then, well, that's another big problem.