Even though Casela may not be considered as small, it is actually really small for elephants. Elephants need to be in constant motion and moving to and fro on a short distance is not really recommended. However, this issue has been partially solved since many zoos walk their elephants throughout the whole zoo before the doors open and Casela's infrastructure with mostly human-accessible path, this solution might not really be applied. The issue of space management should be addressed before bringing in elephants.
However in the world,zoos and animal welfare advocates differ over elephants in captivity. Critics say zoos lack space to house elephants. Zoos argue that they are expanding and improving exhibits, and that elephants live better in captivity than in the wild with disease, drought, habitat loss, poaching, and conflicts with people. Well, even though elephants should remain in the wild, it might be better to have them in zoos, away from poaching, than being affected by poachers.
I hope this reply helps!