Chinas' invasion/occupation of Tibet is payback from the time when Tibets warriors spread thru China plundering etc.
Think about it for 5 minutes, how do the poor ol' Tibetans support themselves and the construction and maintenance of the massive monasteries and feeding all those monks in an environment of extreme high altitude and cold allowing only some limited growing of barley and brewed tea with yak butter? And no trees? So where did all the wood come from?