He was writing for Dr. Dre, he didn't need battle rap.
Guys like Rain are never gonna be big industry stars. He's gonna make music that will have a small core fan base and make most of his money writing for big artists. That's how guys like Rain eat.
Not saying you're wrong but he obviously wants to be known as a solo act. That's the end game he's pursuing. And battle rap/ Smack URL is helping him get on in a major way
Even with the fans not liking him initially, they know who he is. which is more than can be said for 98% of mixtape rappers out there