I cannot add a lot to the good comments made above. I can definitely see the difficulties faced by Atlantic Coop and it could not have been an easy time. Unfortunately, it is easy to see how the decisions that were made alienated the local members and how this ultimately led to the failure of the coop.
As has been indicated by others already, I believe the first mistake was the move to the discount model as it made it easy for competitors to emulate with greater resources. As coops we need to be focussed on what makes us sustainably unique from our competitors. Atlantic Coop lost sight of this. They had early successes but ultimately the vision led to the failure of the coop.