Young people spend alot of time on tick tock. At the level of detail that social media companies can get, they can estimate fairly accurately what issues that people get concerned by, and their opinions. Then they can micro target individual subpopulations with messaging that particularly works at influencing them.

This is very different than historical propaganda efforts, were one had to target the largest common denominator.

Now you can send individualized messaging towards individual subgroups. You see some of this with politicians in the US saying one thing in a set of Facebook adds, while saying the opposite in another set. Because the ads are targeted, neither group sees the ads meant for the other group, Which allows for better tailoring of message.

On top of this the goal of a theoretical Chinese propaganda campaign is not necessarily to send a particular message, but to polarize and divide the country to make it even more disfunctional.