It could be that the boys somehow provoked the butcher or got in his way. Or perhaps there's a deeper, darker backstory to the butcher's actions that hasn't been fully revealed yet.
It might be popular because it stays true to the essence of Aang's character. Fans who love the original show and Aang's pacifist nature would be drawn to it as it explores that side of him further.
Billy doesn't kill Homelander in the comics. The interactions between them are more nuanced and don't end with Billy being the one to cause Homelander's death.