There’s an excellent book called “Autopsy on an Empire” (Warning: long) by the US Ambassador to the Soviet Union when it collapsed.

One of the things that I learned about what the role of nationalism in the collapse of the Soviet Union. Or, put plainly, Armenians don’t like Azerbaijanis, (& vice versa) and nobody liked the Russians. Especially the Estonians, Latvians, and Lithuanians.