Most celebrities look for any media attention that they can get. Chance the Rapper will benefit from Beyonce crashing the interview. It was a polite and friendly brief encounter between the two music stars. The sharing of interview time demonstates that celebrities can help boost the career of fellow artists and they do not have to be selfish with publicity time.
First of all it is a rapper or entertainer's dream to get the kind of publicity Queen B brings to the table. She has millions of followers that are loyal to anything she sells or promotes. A nod from her can change someone's life overnight. He is very lucky to have been crashed by her.
Yes, Beyonce's appearance during Chance the Rapper's VMA interview helps his career because anytime she is in appearance with another celebrity or up-and-coming star, the tabloids and media publicize the event. Beyonce's influence and presence alone offers publicity, which is why Chance the Rapper may now be more well known in the music industry.
Nobody would have been talking about Chance the Rapper's backstage interview without the drop-in by Beyonce. This keeps Chance in the headlines and will certainly allow him to get more work going forward. Hopefully he's putting together a plan to return the favor to Beyonce when he gets a chance.