There are Tibetans and Muslims in Xinjiang that didn't want to be ruled by the Chinese. For Tibet, those monarchists (because that is what they were and still are) took their shot at counter-revolution and failed, and when they failed they ran away to complain in luxury in the West like every comprador class before them. They sought to use their own authority to retain power and failed because, honestly, the peasantry was pretty sick of their shit.

Within Xinjiang, the popular sentiment was with joining with China, because the alternative was becoming a completely land-locked country at the mercy of it's neighbors, far better to ally with the regional power. In the light of multiple devastating terrorist attacks that primarily killed Xinjiang Muslims, mandatory education for adults was installed, and the facilities to bring about that policy was made, alongside checkpoint systems across the region (a system that would be re-used in order to combat COVID a decade later). There were no genocides in Xinjiang, no U.S. style door-to-door raids and mass arbitrary imprisonment of military age males. You either showed up to school or you were sent to jail, so most showed up. And it's been effective because there have been no terrorist attacks since these policies were implemented, even as they have been wound down by the state.

If Hong Kong gets self-determination, it might surprise you to learn that the majority would probably vote to join China. We can guess that because the majority faction within the Hong-Kong government is the pro-CPC faction, unless you are meaning to imply that Hong-Kong might not be a bastion of freedom and democracy (which is where my money is honestly).