Negan knew that maggie had always hated him. maggie was going to have
To swallow her pride and put aside her feelings for him for the sake of her son Herschel who was taken from her one of
Negan's men from when he used to be the leader of the SaviorsHe reluctantly agreed to help her even though she hated him negan would do anything for maggie or her son after all it is his fault that Herschel doesn't have a father in the first place ever since he killed Glenn in the line up not knowing if maggie was pregnant at the time
Negan felt like shit because of what he did that night all those years ago but he wasn't going to let an innocent kid die because of because of his actions
especially Maggie's son no matter what it took he was going to save Herschel on way or another and if he had to die saving him so be it he deserved it anyway after all the shit he had put maggie through .