Because Arthur has gradually been disappointed with Dutch, he has seen clearly the essence of Dutch: hypocrisy, indifference, and selfishness. Before, he could still play the role of a good big brother, but as he survives, The pressure became more severe, and Dutch gradually shed his disguise, and his true nature was gradually revealed. His true heart was completely different from what Arthur imagined.

So if Arthur is not sick, it is inevitable that he and Dutch will part ways, because they are not the same type of people with the same values. Whether it was out of respect for Dutch before or disgust with what Dutch was doing now, Arthur would not take action.

Extended information:

Micah is a traitor who betrayed the gang. Arthur once rescued him, but he beat Arthur to death and felt uncomfortable. John finally beat him to death. he. Micah and Dutch are actually quite similar. They are both people who are unwilling to live a stable life. They especially like to cause trouble. He wanted to be loyal to Dutch, but Arthur looked down on this evil man and didn't think well of him. Facts have proved that Arthur was right. This man did have some little ideas of his own. He wanted to be Dutch's right-hand man. , and this person extremely likes to show off himself.

Micah is a professional killer with an extremely unstable temperament. He has not been in the gang for a long time and is rarely in the gang. He pursues the ideal of freedom with Dutch and Arthur, but Arthur finally gave up, which may have been a factor. On several occasions, Micah tried to drive a wedge between gang members and Arthur, and also taunted him. Maybe Arthur didn't trust him and was always wary of him, so he would definitely hate Arthur in his heart.

In the end, the identity of the traitor was revealed by Arthur. When you go to get money at the end of the game, if the player's honor value is relatively low and he is a bad guy, Arthur and Micah will be killed in a duel, so he kills Arthur. In the ending, Micah also died, just like he said he was a loser.