Ignore the final 7 minutes of Q1 and the Celtics win this game. The defensive switching isn't the problem since they did it the entire game. LeBron is going to get points against any type of defense you throw at him.... Switching causes him to settle for more jump shots than any other defense does. LeBron makes those shots, hats off to him, but it is his worst shot to take.
The more concerning thing is the Celtics missed 3 wide open dunks and many, many layups. If they make even half of the missed layups / dunks they win the game.