TikTok doesn't seem to care about what you "say" you like." They watch your behavior to see what you actually like.
So you can "want" to be shown math videos and like tons of math videos and follow dozens of professors. But if TikTok observes that you are more likely to watch a professional wrestling video to the end, then that is what you'll be shown.
What you want to watch and what you actually "feel" like watching are not the same thing. Other engines show you what you want to watch but don't feel like watching, TikTok shows you what you feel like watching but not what you want to watch.
This same philosophy is observable when you try to exit the app. If you are on the screen the app opens to, the expected behavior of the back button is to exit the app.
TikTok however, doesn't care that you "want" to leave.
They know that it's important for you to leave so now is the time to show the video that they know you will find most irresistible. So when you try to leave they give you the "ultimate" video which you have been conditioned to expect to be "perfect".
In order to leave, you must fight this conditioning and reaffirm your desire to leave within a tiny span of time (feels like less than a second). If you miss the window and try to exit again, TikTok tries to hack your brain again by changing the video for the next video it thinks you'll stay for, and so on...