That’s the nice thing about sea drones only needing to make one, one way trip, and the Black Sea is at most 730 miles or 1,200 km wide. As long as Russia keeps her navy in the Black Sea, there is nowhere for them to hide, and no good options to protect their fleet.
The Black Sea Fleet is the second smallest Fleet. The Pacific and Northern fleets have 90% of Russia’s naval strength, and that’s what Russia is beefing up.
Russia is evil (and Communist), but it’s not stupid.