Well, first of all she's one of the best singers in vtuber community, so her songs/karaokes are abound to bring many (not that she does karaokes often)
https://www.youtube.com/watch?v=aQT0QWi7NWchttps://www.youtube.com/watch?v=4eTbqidnfdUNext, she's funny as fuck, while at the same time there's not many vtubers with similar sense of humor, so people who like her doomer self deprecating jokes, or roasting viewers without mercy are likely to stay.
Even if you don't like this kind of humor, she also has natural talent for jinxing herself, which combined with her being not that good at games creates plenty of funny situations
The fact that she's not good at games is also an important factor at collabs, since she's often a natural force of chaos, either by not understanding game rules or just being a little gremlin messing with others, her pov is bound to be entertaining.
Finally, her zatsus are really good, she tends to go on tangents pretty often and really likes to tell stories from her childhood, which was so fucked up with her asian parents being as asian as possible. Also she holds a plenty of retarded worldviews yet despite that she feels the need to share them and 'educate' viewers, which is stupid but also really funny since she seems like she's serious about it.
