It is just my interpretation and hope you take it that way. I am not a lawyer of any kind.
It is not that obvious.
According to CAPIC, quote:
"Copyright is comprised of international laws that protect “intellectual property.” These laws, which vary from one country to another, also apply to patents, trademarks, industrial designs and trade secrets.
In short, Copyright protects the expression of original ideas, but not the information itself. This expression is referred to as “work” or, in the case of photos and illustrations, “artistic work”. Copyright consists of a set of rules on how the “work” can be used."
The photo is that good thanks to all the "creativity" parameters and events that took place, whether they are on purpose or circumstantial. If any of these factors was different it would be a different photo, a better or worse. Among other things; the choice of camera, the lens and focal length, the aperture and shutter speed, the ISO, the vantage point, the distance from the subject and so on.
On one hand, who ever chose the camera, the lens, brought the it there, turned it on, configure its parameters and so on takes part in creating the result. If he configured it differently, the photo would be totally different and might or might now win anything.
On the other hand, who ever chose the vantage point, the stability of the camera, its distance from the focusing point and so one contributed to its success as well.
My opinion, there are 3 key components in the content of the copyright law: 1- action, 2 - artistic creativity, 3 - intellectual property. Finally, let's not forget its purpose which is to promote creativity.
Unfortunately, the photographer had the idea and contribute greatly in the "artistic creativity, but didn't take the photo and as such is not the sole creator of the tangible art, despite the creative contribution.
On the other hand, giving to the monkey the right to the photo doesn't promote any creativity at all. No photographer would work that hard so that his right would be given to a Monkey. No photographer, no creativity, no photography, no improvement, nothing to promote, empty law.
Besides, I don't recognize any intellectual contribution that is worth protecting in the monkey act (or the assistant just pressing the button of a camera on a tripod).
My opinion, the photographer owns it, at least for the sake of encouraging him to push monkeys for selfie.
Anyone else wanting to take that privilege is just a thief wanting to take advantage of his hard work.
In Canada, the photographer owns the copyright, not the employer - See CAPIC website for detail:
"The Copyright Act was amended in the spring of 2012, under Bill C-11, rectifying the injustice that prevailed hitherto, while the copyright of photographs that were ordered belonged to the client by default.
Canadian photographers are now, by default, the first owners of the copyright of the images they produce, as are illustrators, musicians, painters and writers with their respective work. This applies to both photographs commissioned and paid by a client, and to photographs taken for non-commercial purposes."