“survival of the fittest” was actually coined by a political economist, Herbert Spencer, to explain how lassiez-faire economics produces better companies. Darwin didn’t extrapolate to that in his theories and the quote is often applied to explain how evolution works, but that may not be the case. We can say that evolution results in change but that there are no guarantees that those changes result in fitness of the organism. We can only say that sometimes they obviously do and in other cases we can make up “just-so” stories to explain stuff in terms of fitness.