"If you want a picture of the future, imagine a boot stamping on a human face—forever."
George Orwell (Eric Arthur Blair), Nineteen Eighty-Four
Orwell's Nineteen Eighty-Four is brilliant, terrifying and useful. It's been at its best fighting against governmental intrusions, and is often quoted by journalists and even judges. It's cultural impact has been immense. And, hey, it's well written.
But that doesn't mean it's accurate as a source of predictions or counterfactuals. Orwell's belief that "British democracy as it existed before 1939 would not survive the war" was wrong. Nineteen Eighty-Four did not predict the future course of communism. There is no evidence that anything like the world he envisaged could (or will) happen. Which isn't the same as saying that it couldn't, but we do require some evidence before accepting Orwell's world as realistic.
Yet from this book, a lot of implicit assumptions have seeped into our consciousness. The most important one (shared with many other dystopian novels) is that dictatorships are stable forms of government. Note the "forever" in the quote above - the society Orwell warned about would never change, never improve, never transform. In several conversations (about future governments, for instance), I've heard - and made - the argument that a dictatorship was inevitable, because it's an absorbing state. Democracies can come become dictatorships, but dictatorships (barring revolutions) will endure for good. And so the idea is that if revolutions become impossible (because of ubiquitous surveillance, for instance), then we're stuck with Big Brother for life, and for our children's children'c children's lives.
But thinking about this in the context of history, this doesn't seem credible. The most stable forms of government are democracies and monarchies; nothing else endures that long. And laying revolutions aside, there have been plenty of examples of even quite nasty governments improving themselves. Robespierre was deposed from within his own government - and so the Terror, for all its bloodshed, didn't even last a full year. The worse excesses of Stalinism ended with Stalin. Gorbachev voluntarily opened up his regime (to a certain extent). Mao would excoriate the China of today. Britain's leaders in the 19th and 20th century gradually opened up the franchise, without ever coming close to being deposed by force of arms. The dictatorships of Latin America have mostly fallen to democracies (though revolutions played a larger role there). Looking over the course of recent history, I see very little evidence the dictatorships have much lasting power at all - or that they are incapable of drastic internal change and even improvements.
Now, caveats abound. The future won't be like the past - maybe an Orwellian dictatorship will become possible with advanced surveillance technologies. Maybe a world government won't see any neighbouring government doing a better job, and feel compelled to match it by improving lot of its citizens. Maybe the threat of revolution remains necessary, even if revolts don't actually happen.
Still, we should refrain from assuming that dictatorships, whether party or individual, are somehow the default state, and conduct a much more evidence-based analysis of the matter.
[Edited heavily because I mixed up my responses first, sorry.]
I think there's a selection bias here. When we look at the worst recent dictators (Stalin, Mao) we see that their successors were less despotic. But that's because we selected the most despotic outliers, so of course there was regression to the mean afterwards. We could as easily ask: when Stalin or Mao were rising to power and still weak, why did they turn out to be more despotic than their predecessors?
Also, the states that Stalin and Mao built were stable, even if successorship wasn't clear. A weak successor can seek support from a court party, the army, the rich, the church, or other privileged groups. All these groups are often united against the broader population, no matter what faction they support in court politics.
Many monarchies have had weak or contested successors, or outright succession wars. And many dictatorships have had strong successors who were just as despotic once they established their rule. So I don't think monarchies are more stable as a rule, not without seeing a quantitative analysis.
Do we have many examples of relatively stable regimes that suddenly got a lot worse? Robespierre, Stalin, Mao - they all came to power in a type of revolution (and Hitler came to power in a very illegitimate democratic regime).
Maybe some of the monarchies, thinking about it... but the worse examples still seem to be just after regime changes.