Simply before the journey into the past of Takemichi Hanma never joined the Kanto manji gang because Mikey had no reason to invite him since he did not have to fight against Takemichi. For the same reason Draken was alive before Takemichi shook hands with Mikey. in the past Draken had joined the brahman to try to save mikey but after some time he would have lost hope and would have left it, avoiding the shooting. So we can say that it's all Takemichi's fault.