No Dutch was already insane from the beginning and the Pinkertons have shown to be pretty efficient in tracking down the gang whenever they left from camp to camp.
While Hosea’s death is a major point of the gang falling apart i think even if Milton didn’t kill him he would have died around red dead redemption the mission or would have been hunted in the first game if he didn’t stay at bleechers hope with the marathons and uncle or disappear like Charles and Sadie
Don’t forget that Dutch was already slipping. When they picked up Micah, it was over for the gang. He got in Dutch’s head so bad that not even Hosea could have stopped his madness
