going after chief is their contingency plan i believe since hes awol right now and theyre going through an ass load of trouble to make this fake origin story about him and they cant even take the risk of letting his real childhood story come to light and if they do kill him (i crack myself up sometimes) then they can just say hes mia on a covert op he was running since thats what hes been doing since the end of halo 4, halsey is in some shit mostly from things i cant recall right now but i know shes already fallen from grace with oni and to top it off im pretty sure she defected to the covenant so i think osman has a reason to go after on top of all the personal ones