TLDR: Imu wanted to kill Shirohoshi, and wants to kill Joy Boy. Imu ordered the WG to destroy Fishman Island, in order to destroy Joy Boy's (Luffy's) territory. Luffy destroyed Fishman Island, by becoming such a threat to the WG, that they decided to destroy his territory.
Imu had a portrait of Shirohoshi with the group of people they wanted to murder. Joy Boy is the WG's greatest enemy, since he is based on liberation, while the WG is based on oppression. Luffy was said to be the one to destroy Fishman Island. But, Luffy would never do that. Luffy would never do anything to threaten the Fishmen. He loves them. The only way Shyarly's prophecy makes sense, is if Fishman Island is destroyed by a force outside of Luffy's control, in response to something he did.
Imu and the WG will destroy Fishman Island, to declare war on the new Joy Boy/Luffy. However... I think something truly beautiful will happen.
For so long, Garp has been under the WG's boot to some extent. He watched his son die, because of them. Garp was last seen in Fishman Island. I think Garp will finally snap, and save the Fishman from the WG's attack. Fishman Island will be destroyed, but the Fishman will arrive in Wano, to see the Dawn.
Imu had a portrait of Shirohoshi with the group of people they wanted to murder. Joy Boy is the WG's greatest enemy, since he is based on liberation, while the WG is based on oppression. Luffy was said to be the one to destroy Fishman Island. But, Luffy would never do that. Luffy would never do anything to threaten the Fishmen. He loves them. The only way Shyarly's prophecy makes sense, is if Fishman Island is destroyed by a force outside of Luffy's control, in response to something he did.
Imu and the WG will destroy Fishman Island, to declare war on the new Joy Boy/Luffy. However... I think something truly beautiful will happen.
For so long, Garp has been under the WG's boot to some extent. He watched his son die, because of them. Garp was last seen in Fishman Island. I think Garp will finally snap, and save the Fishman from the WG's attack. Fishman Island will be destroyed, but the Fishman will arrive in Wano, to see the Dawn.