There is dialog in the game that doesn't match what actually happened. On the mountain Dutch says, "You shot at me" if you talk to him long enough, which isn't the case. No one (from the gang) tries to kill each other in the scene where John returns from the train robbery (accept Micah killing Ms. Susan Grimshaw). Maybe the storyline would have had better continuity if there was an actual shootout between the gang where Dutch, Micah, Bill, and Javier were on one side and Arthur and John were on the other just prior to the Pinkerton ambush. However, the only thing you get out of the scene where John returns is Micah killing Susan and Micah, Bill and Javier deciding to stick with Dutch. However at no point did anyone shoot at anyone else during that interaction because they were interrupted and attacked by the Pinkerton gang during their Mexican standoff and John and Arthur ran into the caves at that point. No one really knows what would have happened had it not been for the Pinkerton attack.
I feel like R* tried to give you a complete stand-alone ending with RDR2 by having Micah being the bad guy that gets what he deserves in the end, Dutch gets to walk away with some redeeming qualities after shooting Micah, and Bill and Javier become footnotes to the RDR2 ending. It's like they totally forgot that John is going to end up tracking down and killing Bill and Javier, and that Dutch tries to kill John on sight every time he sees him from now on. Dutch even shoots John the first time he sees him in RDR, although it is from so far of a distance that it doesn't kill him. They pretty much ruined the storyline of RDR for the sake of wrapping things up in RDR2. The OG RDR players know what happens next and everyone else can either play RDR after finishing RDR2 or go on YouTube to see how things played out with Bill, Javier, Dutch and John.
You should want to play RDR again after finishing RDR2, but after the way they ended RDR2 I kind off feel like John got what he deserved at the end of RDR. He turned his back on his former homeboys that were really no worse than he was by hunting them down and killing them for the government. Why wouldn't he expect that the government would merk him once he'd taken out the remainder of his old crew?