BOSTON — The Boston Celtics looked to be doing the thing everyone expected them to do, going up 13 in the third quarter, but they were out-scored 63-34 after that, scoring just 11 points in a disaster fourth quarter, losing Game 5 113-97, forcing a Game 6 in Philadelphia Thursday night.  Here are six reasons why they lost  The Celtics “messed around with the game” They had a 13-point lead in the third quarter and then they started to try to make individual plays rather than move the ball and put the Sixers away. What is this from Jaylen Brown ? pic.twitter.com/kJeZpD5JOu — John Karalis (@JohnKaralisClip) April 29, 2026 Look at who he had open.  Screenshot The Celtics had 18 assists at halftime. They had seven in the second half. Of course, you have to hit shots to get assists, but you also have to move the ball to get shots. The Celtics did neither in the second half.  “I thought we had a decent first half,” Payton Pritchard said.…