Aside from that, they are also nervous about the people. The Chinese government is not loved by the Chinese people, just like the US govt is not loved by Americans.
Americans always used to ask, "Why don't the Chinese/North Koreans/ whoever just rebel?" Maybe now you are starting to see why. The first to fight back are taken down hard, and destroyed. A lot of lives are lost or destroyed before a revolution succeeds (and that's even if it succeeds). Xi and his thugs are worried about their control over their people first. Then they have this fantasy of world dominance where China is restored as the global leader - that part is not rational at all, it's all pride and emotion. And it may end the world as we know it.