Boyle was sent out in game 1 to specifically intimidate Karlsson. Ottawa should've responded immediately on Boyle but for some reason waited until game 2. By that time you could see the thought of getting hit by Boyle was in Karlsson's head. Yes, Karlsson was somewhat dangerous that series, but he wasn't nearly as dominant as he was during the regular season.
Honestly, smart move by Torts to get into the head of the biggest offensive threat on the Sens, and a bit of damage control by the 'Stache in game 2 to try and reverse it.