Where is TikTok not maximizing monetization? If you mean the GP's comment on China's ban on the algorithm originally used then you are missing a critical aspect of that: It wasn't TikTok's choice to stop or decrease monetization there.

Also, even if they were differently monetizing by region, you are also missing the non-monetary reasons this might happen: Manipulation & propaganda. Even aside from any formal policy by the Chinese govermnent self-censorship by businesses and individuals for anything the Party might not like is very common. Also common is the government dictating the actions a Chinese company may take abroad for these same efforts in influencing foreign opinions.