The CCP looooves to oppress people. That's its favorite pastime. But the CCP doesn't oppress Tibet out of love alone. It also has three strategic reasons for maintaining tight control over Tibet. That's in the episode.
There's also a part that didn't make it into this episode. When I was doing research on whether Tibet was "historically part of China," I found that China did have legitimate claims on Tibet during two periods: the Yuan Dynasty (1271–1368) and the Qing Dynasty (1636–1912). But ironically, these were the only two dynasties where China was controlled by foreign powers (the Mongols and the Manchus). And China did not have control of Tibet during any of the other numerous historical dynasties. Just food for thought.