The way I see this is in terms of attractors (in the sense of dynamics).

The dynamics are characterized mostly by institutions and rules rather than ideology.

The idea of liberalism was to get the institutions correct and so create a stable democracy.

If you destroy the institutions then the ideology behind why you did it doesn't matter. Just like it doesn't matter why you remove a load bearing wall in a building. You're at the mercy of primate emotions and everything tends toward oligarchy. That was just as true in the Soviet Union as in countless other countries throughout history.

Oligarchy is an attractor, and you need careful planning to avoid the whirlpool.