The thing about authoritarian regimes, is that they are brittle. They show absolutely no signs of bending, right up until the point that they break. Of course, most of the time, they don't break at all. They withstand the stress, without bending at all, and eventually the stress goes away.

The tricky thing is, a brittle regime that is about to break, looks (from the outside, at least) exactly like one that is not going to break. You can rationalize after the fact why this uprising succeeded, and that other one failed to change anything, but I'm not sure that is was the case that the one was guaranteed to succeed and the other fail. Is China about to see a regime break? Or just hold out, refuse to change, and prevail unchanged? I think, it is not possible to tell from the outside, and maybe not even from the inside.

All of which applies to Iran as well, btw.