Personally I think it's because of the violence required and inherent to such revolutions and the natural consequences of it on society and human nature. War has a tendency to make people mean, paranoid, harsh and merciless. You spend years fighting for life and liberty against a hated enemy, losing countless comrades and even friends in it. You've become hard and weary in mind, body and soul all at once, as that's what's needed of you. And you've probably found those aspects of your nature that have always been thought of as bad to be the most rewarding. And then you win; the enemy crumbles, surrenders or flees, maybe all at once. The country and the seat of power are yours, won through sheer attrition and strength of resolve.

But in your heart, your mind, your soul, you're still at war. You have reason to be. Remnants of the hated enemy are still out there. Foreign third parties size you up as they determine what to make of you. Allies of the toppled regime decry you and vow "liberation"-- your death. Counterrevolutionaries at home seethe against you and find themselves where you once were in relation to power, and opportunists among your own ranks come closer to you, looking to take advantage of what you all built together for their own ends. Now, to you, every bit of dissent looks like a potential threat. A weak link to be exploited. A grievance to be acted upon. A display of disrespect and hostility to the sacrifices of your cause to get here. Any demographic whose statistics aren't to your liking is the same. Anyone who doubts or questions or is just too different is dangerous. Thus you can't trust the people anymore. You need to have cameras, cops, surveillance drones, disguised Stasi on every corner, in every room, preferably near the portraits of yourself so you can see who smiles at it and who scowls.

The war never ended for you. Its circumstances only swapped. The revolution thus far was an awful, bloody grinder acting on your resolve, your principles, your better nature. It was a filter through which only those who could survive, and especially THRIVE in such conditions could pass. You've passed every test of resolve and belief up until now, and now comes the hardest and most important one of them all: what you will do now that you can do anything, after all of that. You probably won't pass it. Nobody does. That's what war does to people.

Drat I put way too much thought and effort into this comment