Ukraine

Perhaps the "correct" way to view the collapse of Russia is like the Ottoman empire. The ottomans fell apart in stages over 300 years, gradually losing direct control and influence over the hinterlands, then suddenly in quick, sharp wars against their former vassals in Africa and the Balkans. Eventually, they end up with a relatively small rump state in Turkey. I think that's possibly the most likely outcome with Moscow/St. Petersburg retaining a much reduced ethnic russian rump state and nearly everything else breaking away. But - the point is - it happens slowly, in stages, and in response to losing wars. Longer than single human lifetimes, so it makes it harder to recognize and comprehend until it's all over.