Simply put, a killer whale cannot be "tamed." You cannot make a killer whale do anything. It is simply too large. It can swim away if it wants to. It can grab you and swim off with you, drowning you in the process. So, progressive animal trainers had to develop new techniques to train these animals.
They had to learn how to coax these large animals to do what they wanted. Because it is impossible to tame such a large animal, they would have to train it.This post was inspired by the book "What Shamu Taught me about Life, Love and Marriage" by Amy Sutherland.