China is emphatically not stable. The PRC was started in 1949. The US civil war ended in 1865. Revolution is a living memory for some in China and that does a great deal to help the population think that suppression at all costs is reasonable. While the US was having its civil war, China was suffering through the tail end of [1]. Historically (in the modern era), China may best be seen as a very violent place.

[1] https://en.wikipedia.org/wiki/Hong_Xiuquan

(Edit: I didn't notice the word superficial at first, it may have been inserted later as a correction.)

They said "superficial stability". The point is that it looks nice and stable if you don't look too closely.