I listened to this while I was in the car yesterday. It would seem that the area they were in is about the size of 3 football pitches. Usually a pack of say 5 wolves roam an area of 85 square km, so theres quite a difference there. The point was made that usually the wolves would run away and therefore the dominance of the Alpha would be established, not just by killing the other competitors as is the case in their small area where they cant escape.
Putting aside the rights and wrongs of having the wolves there
The keepers were in the position of having the wolves tear chunks out of each other and it would seem gradually destroying each other over time as they fought. IT doesnt seem that they would have a fight and one would die, it was prolonged. The decision, right or wrong was to stop the suffering of the wolves because they were getting so damaged.
Theres lots of issues with this but I can see that the keepers were between a rock and hard place. The Wolves were acting naturally, but it was getting extreme because of the unnatural environment. Id not like to be in the position they found themselves, its a loose loose one.