A lot of discussion around Tibet focuses on its regressive feudalistic practices which elsewhere would have been the perfect pretext for the US to bomb the place to smithereens. While that justification in favour of China makes sense, in my view the more important aspect is that Tibet was sort of a poisoned well scenario because the US was using it as a breeding ground for destabilising elements against China: https://en.wikipedia.org/wiki/CIA_Tibetan_program

At such a point liberal talking points about China being expansionist or imperialist when they toppled the Tibetan theocracy become moot because Tibet had become an existential threat to them. What China did to Tibet was literally was any country would have done in a similar scenario and they did it with much more restraint than for example the US.