The NBA is enormously popular in China and an NBA blackout would be catastrophically unpopular. Furthermore, it would be unpopular with precisely the most damaging kind of people, the ones who are largely apolitical but just want politics to not interfere with their daily enjoyments.

There's a common misconception in the West that because China is an authoritarian state, it doesn't need to care about happiness of its citizens which couldn't be further from the truth. The CCP's legitimacy derives from the consent of the governed and the Chinese people know that.