a) China is a de-facto dictatorship, with no independent press or judiciary, who is right now committing mass genocide with the Uyghur muslims and has a long history of kidnapping both citizens and non-citizens abroad e.g. in Hong Kong and Australia.

b) TikTok has been collecting a LOT of data including your personal details, contacts, location, WiFi networks etc. It's not just stupid videos it was everything they could get which on Android at least is a lot.

c) Given the history with previous Chinese owned companies and with overseas companies operating in China there have been requirements that data is made accessible to the government.

China right now monitors users behaviour online and kidnaps them for "re-education". We should not be giving them the tools to keep doing that.