Should re-wilding species be keystone species? How could re-wilding be made successful?

Yes, I think rewilding species be keystone species, such as the beaver, the lion, the horse. If not, than the keystone species could be wipe out and become extinct. These keystone species are important to the environment and to us. Rewilding can be made successful by releasing the animals caged in the zoos, or to simply stop hunting them.