Why? You fail to mention your assumptions about Luxembourg judges that underlie the "plausibility" and "unsurprisingness" of this outcome. Can you maybe share your argument with the curious reader?
The court argued that the original photograph was not original enough to warrant copyright protection.
Yet a painted replica of the photograph was apparently original enough to win a prize and be put up for sale at a gallery.
This decision is completely absurd, so there must be some reason why the court decided the way it did.
The explanation that a Luxembourg judge at a Luxembourg court decides in favor of a Luxembourg man who just won a Luxembourg price and is represented by a popular Luxembourg lawyer just sounds very plausible.
Judges are humans too, and they are not infallible, so it seems plausible that this has something to do with the decision.
Yes, there must be a reason. It's described extensively in the proceedings of the case.
What seems most plausible to me, is that we, aliens to Luxembourgh copyright law, outsiders to the court case, unaware of the actual text of the ruling, jump to unfounded conclusions based on our gut feeling and superstitions.
You seem to have a lot of trust in the Luxembourg district court :)
Maybe there is something in the proceedings that explains the absurd ruling, but I really doubt it. We'll see how the story plays out. I don't think this judgement will hold.