Combination of a lot of things.
>Post DB/Sailor Moon boom for kids of that generation that brought in another wave of anime fans
>All began airing around the same time in a much less competitive market compared to today
>Absurdly long in comparison, Naruto has 500 episodes, One Piece has over 1000, Bleach is over 300 I'm sure, each one having 70+ volume manga runs and a shit ton of movies, compared to rough 50 episodes of JJK and KnY, alongside having far less chapters and movies, alongside other spin-off material like games
It's just a fundamentally different market with far more competition. Anime is more popular than ever in English speaking countries, but there's far more competition in it (beyond just anime too) and the shows don't go on for nearly as long.

>>715620335
based