User blog:Videogamep/Why is One Piece so Popular?

As the title says, I want to know why you guys think One Piece is so popular. Nobody asked a similar question with his recent blog but I want to know why it is at the top when there is a lot of competition. As this article shows, it sold over 2,000 more copies than Attack on Titan, even though that is much newer and has gotten a lot of hype recently. Most series would start to loose popularity after 13 years, but One Piece has been at the top for several years. Even when it's sales dropped between 2012 and 2013, it remained at the top. Compare that to Naruto and Bleach, which were bestsellers when they first came out and are now only moderately popular. What did One Piece do to earn all this popularity.