The Boston Celtics' steam engine, which was moving at full speed during Games 1 and 2, surely lost some of it's momentum in the series's last two games with the Milwaukee Bucks.
The Cs were affected by Milwaukee's personnel change in Games 3 and 4, when they gave Matthew Dellavedova and Thon Maker extensive promotions. In the series's first two games, Maker and Della played a combined 6 total minutes, and both received DNPs in Game 1. In Game's 3 and 4, the duo totaled 88 minutes, and created a spark for the Bucks on both the defensive and offensive ends of the floor.