Why shouldn't different or even "opposite" traits also be successful? When faced with random inheritable differences across different species over long periods of time why wouldn't the result be a variety of them, every one of which just didn't prevent reproduction from passing those traits on to the next generation? Some traits might be seen as "better" or "worse" by comparison but as long as they get passed on, we'll see both. It isn't about being "best". It's about being "good enough"