Gazelle can afford to move it's eyes to sides of the head (not being a predator), the fly has near omni-directional vision.

The predators, however, have a problem - they can't move the eyes to sides of the head, because that will lose the sharp binocular vision they need to stalk the prey. So it is predatory species that would benefit the most from a rear view eye. The chameleon evolved very peculiar eyes, but that's the only solution the predatory vertebrates got.

The spookfish evolved rear view mirrors that it uses to look down and up at same time. As well, there is parietal eye, but this one is very ancient and traces all the way back to time when ancestors of those animals were more transparent and it was a straightforward adaptation to add light sensitivity to some cells in the brain.

It is extremely difficult to evolve eye on back of the head. It's rare dumb luck, it takes a lot of generations, and existing eyes don't end up duplicated (except in insects and spiders etc which apparently have more flexible coding for eyes; but even in those this kind of thing doesn't happen overnight).

The point of the example is that it is not enough to show that something is advantageous, to show that it is possible to evolve. Furthermore, thanks for bringing up the gazelles - that serves as an example of how evolution really solves the rear-view problem. It doesn't create new photosensitive modules, or replicate existing ones. It just moves the eyes to sides of the head. Keep in mind that eyes, developmentally, are modules of the brain.

The evolutionary psychologists don't take that empirical knowledge of the ways of evolution into account in any way; that's why i would say they are misusing word 'evolution' to mean 'magic'; the word evolution ought to encompass our knowledge of how evolution works, whereas the magic can do anything.