Despite the word "Wins" in Wins Above Replacement, the outcome of games is not used in any of the calculations for WAR.
https://en.wikipedia.org/wiki/Wins_A...sition_players
Think of it this way, a team could go 0-162, score say... 10 runs minimum in every single game, and most of their players will have top WAR in the entire league.
Unless there is some extra information not presented in the wikipedia page, this formula seems to work under the assumption that players who score a lot of runs are on teams that score a lot of runs and thus, win a lot of games.