I think its more to do with the lack of real options for the role.It took Don that long to break Campo.
We backed in Knight with his tank against selective group of opponents but as soon as there was a bigger match winning midfielder that opposition would roll out we struggled for options.
What Gibson brings to the role is size and versatility. At his size, he can go out there and tag the likes of Martin, Dangerfield, Kennedy etc.... but he can also play on the likes of Selwood, Gray etc...
Gibson can also play as a wingman or HBF thanks to his running ability which adds more versatility to the side. This frees up Knights to either play the small forward role and/or rotate further up the field.