Does it have a connection to Roger? Have you ever wondered why the World Government considered Dragon as the most dangerous criminal? One might say simply because he is the leader of the revolutionary army. That is true, but that is only half of the reason. We know that Dragon was present at Roger’s execution. If you’ve watched One Piece Episode 0, you would know that Dragon was there at Logue Town.
What was the purpose of Dragon there? Also, no tattoo marks were on Dragons face at that time. Thus, it is well possible that he wasn’t a part of Revolutionaries at that time. Also, we know that Ceasar Clown is a brilliant scientist but he’s not smart. He is good at science but not a strategist. He’s simply a clown by nature. Therefore, someone who is a genius scientist is not necessarily a brilliant strategist. But we know how brilliant Dragon is at creating strategies. He is, in my opinion, one of the smartest people in the world of One Piece, and I think he would understand the secrets of Devil Fruits.