This was one of the Justin Bieber “reveals his track listing in graffiti/street art commissions around the world” pieces. KEM5 and DEME5 did the work and, in addition to being able to do one of the most seen pieces in Boston history, I’ve always hoped they made a pile of cash for the work. Those guys are really good.
As for the visibility of this versus other pieces, I imagine that more people saw the Giant of Boston in person, but the Bieber piece would have gotten in front of a hell of a lot of fans in a very short time on Twitter/Instagram/Facebook.