Ya this is classic Celtics trap. they score a bunch largely because they hit a bunch of jumpers. The jumpers stop falling, because the team is bad at shooting. The other team gets rebounds and gets out in transition to score. Celtics get down on themselves, everything falls apart.
We'll see if they break the cycle this game.
Edit: Or maybe they'll just hit every three this game. Probably not a long term workable strategy but all these 3-30, 4-40 games hve to balance out eventually.