The story of One Piece has always been one crazy roller coaster ride, and that is especially true for the Wano Country Arc. Chaos has always been a staple in every One Piece arc, but the Wano arc brings it to a whole different level. There are six pirate captains from the worst generation and two emperors of the sea, along with most of their crews in Wano. There are also the samurais, ninjas, and some people from the minks there.
To make things even more problematic, three members of the World Government's most dangerous and powerful agencies, the CP0, are also present in Wano. Each of the aforementioned factions has its own interest in mind, but none of them are as sinister as the CP0. CP0 came to Wano in order to buy weapons from the Shogun of Wano, Kurozumi Orochi. However, as the conflicts are getting more complex by the minute, the World Government began to update CP0’s objectives. First, they have to capture Nico Robin, and then they have to kill or confirm the death of former CP9 agents who have joined Kaido's Tobiroppo under the name of Who’s-Who. Finally, CP0's last objective is to kill the captain of the Straw Hats pirates, Monkey D. Luffy. But why does the World Government want to kill Luffy?
Maintaining the Balance of Power
For decades, there have been three Great Powers that maintain the balance of powers in the world. The Marine Headquarters, The Seven Warlords of the Sea, and finally the Four Emperors of the Sea. Out of all of them, the Marine, and by extension, the world government, is the one that is obsessed in keeping that balance intact.
However, in the reverie where the kingdoms from all over the world gather once every four years, a major change has happened. By defeating Crocodile and Doflamingo, Luffy indirectly allowed the king of Alabasta and Dressrosa to finally propose the dissolution of the Seven Warlords system. And the majority of the nations of the world agree with their proposal.
Meanwhile, in Wano, two of the Four Emperors are on the brink of being defeated. Once again, Luffy is one of the major catalysts for such an unprecedented event to happen. He seems to be able to influence such a massive shift in power, whether he intends to do so or not. Thanks to Luffy’s action, the fragile balance of powers is about to be broken beyond repair.
An Impulsive Wildcard
When Luffy beat Crocodile, one of the Seven Warlords, the World Government began to pay close attention to him. However, nobody ever thought that he would become such an influential pirate at the time, and yet since Alabasta, the name of Monkey D. Luffy always popped up whenever there's some major events happening in the world.
Luffy is involved in the incident in Enies Lobby, the chaos in the Sabaody Archipelago, the war at Marineford, the uprising in Dressrosa, and many other world-shocking events. When you think that he would finally settle down for a bit, he went ahead and wreaked havoc on Big Mom's tea party. Luffy really is the embodiment of impulsivity and unpredictability.
For the most part, the World Government can predict the movement and intentions of the world's biggest pirates, including the Four Emperors of the Sea. But when it comes to the Straw Hats, they truly have no idea what kind of disturbance Luffy will do next. And in the grand scheme of things, this kind of wildcard is dangerous for those who wish to keep things neat and balanced.
Fear of Luffy's True Potential
Luffy is a man with bottomless potential. Some of it certainly comes from his family. After all, he is the grandson of Garp the Marine Hero, the son of Dragon the leader of the Revolutionary Army, and the sworn brother of the late Fire Fist Ace, the 2nd division commander of Whitebeard Pirates, and also the sworn brother of Sabo, the Revolutionary Army's Chief of Staff.
Beyond that, there's also the true potential of his devil fruit, Gomu Gomu no Mi. According to former CP9 agent, Who's-Who, Gomu Gomu no Mi was the only devil fruit that had to be escorted by the CP9. Whether by luck or not, the fruit was stolen by the Red Hair Shanks, which later on was eaten by the young Luffy.
It is still unclear at this point why the world government went so far as to guard that particular devil fruit. However, recent chapters alluded to the fact that what they are truly afraid of is the awakened version of the Gomu Gomu no Mi, because it somehow has a deep connection to the legendary pirates called Joy Boy.
A Growing Power and Influence
Luffy has a natural ability to attract people and gather them under his banner. The most obvious example of this is when seven infamous pirates swear loyalty to him and therefore form the Straw Hat Grand Fleet at the end of the Dressrosa Arc. He also managed to regain the support of some of the biggest nations in the world, such as Alabasta, Dressrosa, Fish-Man island, and many more.
This massive amount of support means that when Monkey D. Luffy decides to go against somebody, countless powerful and influential people will gladly rally behind him. That amount of influence is a direct threat to the World Government. Because that means, one pirate alone is enough to tip the balance that they've been maintaining all of these years. For the World Government, that kind of power is simply unacceptable.
All of those reasons above combine with the fact that the battle between the two Emperors against the rookies from the Worst Generation seems to favor the young pirates, the World Government is finally pushed over the edge. In a desperate attempt to prevent their catastrophic future, the World Government decides to issue the order for the CP0 to kill Monkey D. Luffy.