> I think one possible reason is that the Qin Dynasty really managed to assimilate everyone into the same shared values, religion, language, writing, and so on. Other empires didn't succeed to that level

Qin conquered the other Chinese states and the ensuing dynasty flamed out immediately. The work of creating an empire was done by the following Han dynasty.

> There's even a famous quote for this: "what is long divided must unite, what is long united must divide"

分久必合，合久必分

https://ctext.org/sanguo-yanyi/ch1

Often given as "the empire, long divided, must unite; long united, must divide", but your translation is much closer to the text, which doesn't mention empires except in that it follows this statement ["They say that across the course of history, what has long been divided must unite, and what has long been united must divide"] with a discussion of Chinese governments schisming and unifying.

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didibus 9 days ago | parent [-]

I'm not an historian or even did any extensive research on this. I thought that the Qin dynasty established a ton of standards super aggressively and also worked very fast to erase and assimilate. Even if it didn't last long, it kind of set the pattern.

	▲	thaumasiotes 8 days ago \| parent [-]
		It lasted for fourteen years, with a sharp drop in stability for the last three of those. No, that's not enough time to do cultural transformation. The shared values, religion, language, and writing preexisted the Qin. So much was shared that the state of Qin considered it a problem - Qin propaganda (before the conquest) tended to emphasize how different they were from the other Chinese states.