Because the inning prior he loaded the bases with no outs and lost the lead. Are you even watching the game?
This looked like a loss on paper but certainly seems like a lost opportunity so far. Late inning magic coming up.
He was at ~75 pitches going into the 6th. It doesn't matter that he loaded them the inning prior. In a perfect world wher your bullpen hasn't been used much then it might make sense to pull him. But not with how much the bullpen has been used. Hindsight is always 20/20