China says that Hong Kong CEO Carrie Lam may not resign because she must remain in power to clean up the mess China started and blames on her. Albeit, staying in power to clean up her scape-goat mess is impossible because cleaning up that mess requires her to resign as the people demanded. The "mess" includes her being there in the first place—because her election was not from self-governance as Hong Kongers were promised in 1984. The mess also includes China saying who may and may not resign—because China doesn't get a say about one grain of sand in Hong Kong until 2047.
The whole problem goes back to China's inability to not meddle. A Beijing-managed group based in Shenzhen has been carefully researching and observing the developments in Hong Kong so that Beijing can know how to properly respond—whatever that's supposed to mean. Make no mistake, they aren't trying to understand how to govern a free people or understand the reasonable requests of a free and self-motivated economy. They aren't trying to learn whatever wisdom might have made the West so rich and powerful in the first place. No, Beijing is on a mission to Sinicize Hong Kong out of being Hong Kong.
The current task is to figure out how to "disappear" 2 million Hong Kongers without the world noticing. Hong Kong's police under-reported the 2 million turnout; they'll probably under-report the number of "disappeared" people as well, and they need research to make it sound convincing. If the protests had happened in Xinjiang, Beijing wouldn't need to do such research because the world wouldn't be watching because making 2 million people disappear in Xinjiang was never a problem in the past. And, that's what Hong Kongers rightly fear.
Beijing's research narrative presumes that Hong Kongers only fear being "Xinjianged" because some phantom, invisible Western influence influenced them. They have no proof of this, but that's Beijing's presumption. If there's a problem, it must be America's fault. So, Beijing's approach is to sneak around and spy from the shadows until this phantom "influence monster" from the evil West shows its face. That's Beijing's plan to solve the Hong Kong problem.
Now, there's constitutional discussion about where and how Hong Kong's "Basic Law" allows military intervention from China, namely if Hong Kong's government asks. But, the whole discussion misses the whole point—that Hong Kong's Basic Law is based on the Sino-British Joint Declaration of 1984 of non-interference from Beijing. Beijing already interfered by not allowing self-governance in Hong Kong as promised. Not letting Carry Lam resign is yet another violation of that promise and premise. So, technically, the law beneath the Basic Law has already been dissolved. And, Beijing only incriminates itself further by claiming that promises made in the past don't need to be kept because they are in the past.
Pay attention because, while Taiwan is a linchpin that will bring America into war with China, Hong Kong is the linchpin that will bring the UK and Europe along with it.