I can only see 3 different ways the Gomu Gomu No Mi can be deemed special:
1- It has a secret only the World Government knows about;
2- A Celestial Dragon wanted it (I think this is the least likely to be the case by itself);
3- It’s special because it counters the Goro Goro No Mi.
Goro Goro No Mi was the only fruit deemed to be “invincible.” If the previous user of the fruit was someone like Rocks, it’s definitely understandable why it would be considered invincible and why the World Government would fear it so much. Also the World Government doesn’t know that Enel has the Goro Goro No Mi devil fruit, explaining why no one in the series has commented on it – they probably assume the fruit somewhere lost in the world.
Oda has said that if Enel came down to the Blue Sea, he would have a bounty around 500 million berries, which I thought was pretty high for someone like him, but makes perfect sense when putting the reputation of the Goro Goro No Mi in context.
Most importantly, I think this theory makes the most sense thematically. The World Government, fearing the power of the most “god-like” devil fruit, wanted to secure and “imprison” the only fruit that can counter it. However, due to fate or sheer coincidence, it was stolen and eventually eaten by the person who would bring the Dawn of the World.
Of course, this ties into the theme of fate that is often prevalent in One Piece, but also emphasizes the that the Will of D. defies the Gods.
I’ve seen some people saying that this reveal would be anti-climactic because we have already seen the dynamic of the Gomu Gomu No Mi countering Goro Goro No Mi, but I see it in a different way. I think this would be a great reveal because it ties the broader story together thematically. It establishes a connection from the very beginning to One Piece to near the end game and the themes I mentioned above.
*Theory by N_xrwhal / Yoradise
