Popularity on decline over the past five years
Checking Google Trends over the past 5 years it shows a steady decline on her popularity:
See: https://i.imgur.com/pCo1vVF.png
I think her change in looks (getting considerably thinner, trying to look more "natural" and honestly less "black") is an attempt to reverse this trend but it isn't working and it has instead accelerated the decline since her fanbase doesn't likes it.
Check the comments on her fan subreddit about recent photos: https://www.reddit.com/r/KylieJenner/comments/19en62f/jean_paul_gaultier_show_in_paris_january_2024/
Guess the hype wave for her is over, seems like it was bound to happen because the trend has been moving away from the "kardashian IG look" that dominated for so many years and people now like more natural looking celebs.