@Monquito:
no-o, everything it was calmed down already after the war at MarineFord, what's happening now it's for Law's actions.
What's happening now is due to the Banaro Incident. What Law and Luffy did are just ripples from it. Big ones at that.
As Law clearly stated, people like Doflamingo merely tried to reinforce and protect the positions that they grew comfortable on. Obviously in Doflamingo's case, it is the selling of SMILEs, drugs, weapons and inciting wars.
Whitebeard ended an era. However, Ace's death meant the Mera Mera no Mi eventually came into possession of Doflamingo who was trying to use it to lure Luffy away from Law's plans. This ended up backfiring since there are now a large and growing number of people with grudges against Doflamingo. Nevermind that the fruit has led to a powerful Revolutionary Army soldier, who is clearly on Luffy's side, joining the fight against Doflamingo. Ace's death was also the prime factor behind Garp's retirement.
Another side effect of the end of the era was Blackbeard's ascension which meant the existence of a person who managed to get two DFs, turning most of Whitebeard's former territories into bloodbaths. And if that is not enough, Akainu became daring enough to move Marine HQs to the New World since the strongest of the Yonkou was dead. Blackbeard's desire for the Shishibukai status led to numerous level 6 prisoners from Impel Down escaping which disgusted Sengoku enough to retire. That led to Akainu eventually taking over as Fleet Admiral which made Aokiji abandon the Marines.
As stupid as Luffy is, he isn't so stupid to accept an alliance with a questionable character unless he absolutely has to (remember his alliance with Crocodile?). Saving Luffy's life during the Marineford War (in which Luffy would have only gone due to the Banaro Incident) did wonders for him to accept. If there wouldn't have been no war, Luffy would have stayed in Amazon Lily and Rayleigh would have still caught up with him.
Fishmen Island would have still be protected by Whitebeard so there wouldn't be any confrontation between Big Mom and the Straw Hats.
It all boils down to the Banaro Incident when Blackbeard gave the World Government a huge card they had to play.
If Ace would have successfully killed Blackbeard or let Blackbeard go to Water 7 to get killed, Ace would have just returned to the Moby Dick and kept sailing the seas while Whitebeard secretly trained him to take over the crew after his death. The Sabaody Archipelago would have been better guarded which could have led to the capture of one or more Straw Hat. Kuma would interfere and still send everyone away to different parts of the world and the two year training would have still gone through. The biggest thing that would have changed is that Marine HQs would have still be in Paradise rather than the New World.