I have to imagine either Tyrese is still hurt or Carlisle thought those matchups (Pascal/Miles) were better for them. Other strange things were done in this game as well (e.g., lots of extended bench minutes).
It has to be injury.
If you are a guard being defended by Beasley, Lilliard and PatBev in his millionth year, it truly isn't going to get much easier than that in any playoff series. The Bucks with Giannis were not a very good defensive team, and their weakness defensively has been in the backcourt. That's about as bad a defensive backcourt as there is in the league.
A 2nd team all-NBA level player getting guarded by any of those three needs to have the ball, making a play every single trip down the court. And if they are doubling a lot, which the started, now you have something to make some hay with from the other guys. But that's not at all what they did. They just got the ball out of his hands and had him play off the ball, with not much motion or action to get him the ball, all while being guarded mostly be terrible defensive players.