Anatoly Karlin. http://akarlin.com/
Interesting hypothetical. Questions-
1. What precisely makes these totalitarianisms immortal? The people surrounding the dictator can change. The dictator himself can die (even with Radical Life Extension, accidents will still happen). Or he might change his mind on certain topics over the centuries and millennia. Eternal goal consistency may perhaps be maintained by a carefully constructed AGI, but this would move this scenario more into the category of X Risks posed by machine intelligence.
2. Romania was more of an elite coup against Ceausescu by the security services, the mass protests were mere backdrop to that. This is incidentally why Ceausescu was executed so quickly, nobody in the Romanian elites was interested in a public trial where their own roles in the regime would be opened up to the limelight. In fact, I cannot think of a single case of a successful revolt against a dictatorship (authoritarian or totalitarian) that was not accompanied by some degree of elite defections. No elite defections - no revolution. (We are seeing that now in Belarus). This point really just reinforces the first issue - the question of how precisely the ruling dictator/authority is to maintain goal consistency over sufficiently long stretches of time. (E.g., even a centuries long totalitarian cyber-panopticon, unpleasant as it may be for its denizens, will not constitute an existential risk if it does in fact collapse or fade away over time).