Jaylen Brown has been named the Bill Russell NBA Finals MVP after the Boston Celtics defeated the Dallas Mavericks, 106-88, in Game 5 Monday to secure their record 18th championship. Brown capped off his stellar series with a 21-point, eight-rebound, six-assist performance in Game 5 to close out the series. Through the five games, Brown posted averages of 20.8 points, 5.4 rebounds and 5.0 assists per game. Brown’s best came in the Game 3 victory, when he tallied 30 points, eight rebounds and eight assists. The three-time All-Star was passed up for the All-NBA team this season, but now has a Fi…