Probably because they began the genocidal sinicization of Tibet in 1950, yet the world largely ignored it while continuing to support the Chinese economy through manufacturing.
Only with the Uyghur genocide of the last decade have nations begun to care enough to criticize, likely due to their production of goods through forced labor.
Maybe the world would’ve cared sooner if they forced the Tibetan monks to make cheap plastic junk for Amazon and Walmart.