Anime fans are used to seeing the same familiar tropes like the genius scientist or the dimwitted protagonist. Based on a character's outward personality traits, it's obvious what kind of person that character is. Someone like Goku is known for being a happy-go-lucky idiot, and Light Yagami is obviously a genius from the start.
Source：https://www.cbr.com/anime-characters-smarter-than-they-appear/
