P.S. Also, not that it makes the situation any less reprehensible, keep in mind that heavy majority of Crimea population at the time of capture was ethnically Russian and was supportive of RF actions. Hong Kong residents, on the other hand, seem to be way less supportive of PRC.
Edit - And this most recent round of demonstrations is the nail in the coffin. No business would ever do business in HK now with the political uncertainty, easier to simply set up shop in Shanghai or form a JV.
This is why the underlying sentiment of Hong Kong independence is especially offensive to Chinese sensibilities.
There was something else still: the population of Crimea was mostly Russian. Like, really Russian. Using only Russian language, calling hryvnas rubles, and in general feeling Russian. Many of these people actually liked the idea of Crimea being a part of Russia (at least before the invasion - things changed a bit since then). In HK the situation is completely different: people know what kind of country China is, and will fight for whatever rights they still have.
We do not know what people of Crimea wanted. Nobody during military occupation of Crimea asked their opinion.
After the invasion cam ethe period of disillusionment. It turned out the situation only changed for worse. But nobody should be surprised there was practically no opposition when Russians took over Crimea.
https://newrepublic.com/article/116814/crimean-tatars-primer...
Crimea is occupated and this is reality. All other talks about how much Crimea is more Russian sounds like a Russian propaganda.
Sure, the topic has disappeared from the news. But that does not mean everything is back to normal. It just indicates the situation is frozen.
More generally, territorial expansion by force has been extremely rare in recent history, compared to previous times. That would indicate that the practice generally being frowned upon, and the available actions in response, are somewhat effective.
As to Syria, I remember hearing about it on the first day of protests. That's not to say it went well in any meaning of the word–there really aren't any good options once a government has decided to brutalise its own people. But it did get attention.