In the interview he just gave to Vibe he says,

“I knew what it was for the culture of hip-hop. You see how excited people are, and I wanted to do that for music make that play happen. It gave me like the feeling of how hip-hop was. How it used to be. When I heard [Kendrick's] verse I wasn’t about to go back and change my verse—that’s cheating. That ain’t the way of an O.G. That ain’t how G’s move.”

Check Big Sean out in this Vibe interview in the video below!