TikTok has two advantages - first, an order more user data to refine it's feed algorithm and second a format that lowers the bar for content creation which allows for super niche content to be viable. The combination enables a feed that resonates.
Their recommendation algorithm is reportedly the envy of many other platforms. I heard that was pretty much what was being bid for at the time offers started floating around.
TikTok always gets a zero or 1 on each video, whereas FB only get interactions for a minority of units. This makes it a lot easier to train better models.