Boxberger and Fulmer at about $7 million between the two wasn’t “nearly zero investment.” They were bad/hurt, and performed significantly below their career numbers, but the investment was there and had they posted their expected 60-65 innings of 3-3,50 ERA baseball, the bullpen would have been a different story.
For whatever reason the Cubs weren’t able to repeat the recent success they’d had with Givens, Robertson, Chafin, etc.