Big Sean?
It's because he's good, but not outstanding. He's a diva on social media in spite of having decent (not outstanding music).
...but the most noticeable difference between him and his peers is that he doesn't really have a big crossover co-sign & backing.
Kendrick has Dre.
Drake has Wayne.
Big Sean has Kanye.
Keef had Kanye.
Cudi had Kanye.
Cole had Jay-Z.
To some degree, Wiz has Snoop.
Wale has Ross...and while Ross is popular, he's not crossover popular.
His co-sign works more for Meek than it does for Wale.