I think the "poor fit" angle is overblown. Brandon was salty they wanted him to move into the slot and prolly voiced his displeasure... Considering the money he's making, they can get slot production out of someone less expensive. My opinion is they thought he may end up a cancer if he wasn't treated the way he felt he needed to be.
Zimm is a coach who tailors his playbook to what he's working with... He could prolly figure out how to use him best while keeping with his defensive philosophies.