He's right about the first bold point. You are incorrect about the 2nd bold point.
Who argues that Kast doesn't connect with fams outside of Hip Hop?
Kast fans and Arrested fans don't intersect? Case in point, there are fans who love Southern Hip Hop, but have never touched or would ever bring up Arrested Development in a discussion on Southern Hip Hop. Same can't be said for Kast. People who like Eightball & MJG and UGK also like Kast. Kast even has songs with them. Same cannot be said for Arrested.
The Fugees inherited Arrested's fan base. That group was like Arrested Development 2.0 right down to having one mega successful album and an album no one cared about (it just happened the other way around for The Fugees). They even remade oldies. Only difference is Lauryn, Clef, and Pras had solo success.