The picture did not capture creative expression of the photographer.
The macaques were simply fooling around with a plaything and had no comprehension of what a selfie is; there is no artistic intent on their part. On the other hand, the photographer by his account appeared to go into this project with the specific intent of obtaining a monkey selfie. The concept, the subjects and their moods, lighting, shot settings, etc. were all his doing, and by any reasonable yardstick his work should be recognized as a form of artistry, just as how it is not exclusively the cinematographer, but the Director as well who is entitled to copyright on a film.
And yet we have people arguing in court that by the legal specifics of who owns copyright on photographs, this is purely the monkey's "work" (and winning).
A monkey didn't sneak into his hotel room and take a happy snap. He sought them out and spent days with them, and handed his equipment to them. That's not 'indirect causality'.
By your reasoning, if I was to put a camera in a tumble-dryer and let it snap photos while spinning, those photos would not be mine because whilst I set up the circumstances, the actual photos were not specifically composed by me.
Far too much emphasis is placed here on who pressed the physical button, and not who brought everything together.
I don't have a problem with that consequence. Copyright is supposed to reward creativity. I don't consider "photo made by putting camera into a tumble dryer" creative in any meaningful sense. I understand that a lot of modern performance art would probably be excluded with this approach - but I don't see it as a problem, either.
That's extremely provincial and 19th century view of the matter.
In modern art all kinds of artists including photographers give creative control to random elements and processes.
It's the setup they built and the creative concept behind it that defines their artwork, not the details like "composition/timing" which they can leave to chance, others, etc. (Yes, in some works even "composition" and "subject matter captured" can be detail left to chance -- this is often the case in e.g. generational music and painting, where the artist just sets up the general framework).
Artists are welcome to do all kinds of things, such as "given creative control to random elements and processes". But they shouldn't be surprised if copyright law doesn't fully apply to the result.
Because it was superseded by 20th and 21st century ones?
In this case, the Work was created by the monkey. Yes, the camera owner helped, but he doesn't meet the established criteria of the Author in existing copyright law. Nor does the monkey (works of nature are not copyrightable).
You can disagree with the law as it exists (I think terms should be drastically shorter, and in no case should copyright be extended retroactively), but it takes an act of Congress or the courts to change it.
What about an artificial intelligence that creates music? Who owns the copyright then, the programmer or the AI?
They didn't represent the animal, they defended a copyright infringement charge, if I'm not mistaken.
And I'm ... rather surprised ... that they were given anything more than "friend of the court" standing in this.