It's spycraft, a way for US culture and influence to penetrate China. It's deliberate.
American Basketball vs. Chinese Hardball: Guess Who Won https://www.nytimes.com/2019/10/13/world/asia/china-nba-cens...
NBA Stars Study Hollywood’s Playbook in China https://www.wsj.com/articles/nba-stars-study-hollywoods-play...
NBA, 'South Park' episodes spotlight Hollywood's China dilemma https://www.reuters.com/article/us-china-hollywood/nba-south...
‘South Park’ creators issue mocking ‘apology’ after China reportedly bans sitcom https://www.youtube.com/watch?v=A1KCVj_v0ik
Band in China https://southpark.cc.com/full-episodes/s23e02-band-in-china
It's interesting how China is turning the globalist policies of developed countries into power. The government bans a cartoon character due to memes and suddenly lots of huge companies start censoring themselves out of fear. The US may have freedom of speech but it doesn't matter if China is the bigger market.
Protip: this is the covert part. Who convinced you that's what's happening? Riling up Americans to make a lot of noise about how "China is totally getting one over on us, we swear" makes it realistic and keeps those things in China as sources of American cultural osmosis. If Disney or NBA "took a stand" then they would get the boot just like South Park did once Matt & Trey took the fall (and ton of free publicity) to prove that possibility is real.
For what it's worth I also absolutely see e.g. TikTok as the same concept in a slightly different domain and operating in the other direction. I don't know where I stand on "banning" it in America since the idea does offend my inner libertarian but China already set the precedent there many many times over.