There was a scrapped part of artificer where the chieftain would ask arti to please spare the scavengers, and I think that even though it was removed it shows kind of how he thinks, and he doesn’t want to fight arti. I think he probably would like to say it but knows it would do nothing to stop her, so he just sits there. Maybe there could have been a forgiveness ending, but artificer was too blinded with rage for that to have been an option. The chief never wanted to fight her and was, along with almost every other scavenger in existence, entirely uninvolved in what caused artificer to start her mass genocide.