Set in 1899, during the twilight of the Old West, “Red Dead Redemption 2’ (“RDR2”) tells the story of the grinding dissolution of the Van der Linde gang. The fate of Dutch Van der Linde will be known to those who played the first game, yet the story of his gang’s earlier days is as engrossing as anything in popular gaming. Whereas “Red Dead Redemption” (2010) concentrated on the wanderings of ex-Van der Linde-gang member John Marston, in “RDR2,” players assume the role of Marston’s fellow gang member Arthur Morgan, a laconic man equally prone to compassion and brutality. Though the world of “RDR2” provides ample incentive to set out alone with your horse — to sightsee, hunt, fish, gamble, or look for weirdos to interact with — the game is hyper-focused on group dynamics. Indeed, the entire thrust of its opening moments is to establish just how beholden Arthur and the rest of his cohorts are to Dutch’s charismatic leadership.