Again, there's a Soviet counterexample of army/party/intelligence service.

Even in the case of a dictatorial and lifetime head of state, separation of powers is baked into the cake by groups with common interests, sometimes organically, sometimes on purpose.

Seperation of powers is necessary but not sufficient requirement for maintaining democracy. In classical Athens they didn't have that, so modern philosophers take pride that we do have it.

Of course any sufficiently big organization does have competing departments with conflicting agengas, but also there are nuances.