I just saw a short twitter mentioning it and didn't researched further. But the essence is the same. AI art itself can not be copyrighted, art needs a human behind it to claim copyright.
I did some googling about to see if I could understand the case better, and apparently the story itself was using a celebrity as basis to make the main character of the story be consistent throughout panels, so that may have influenced the case.
The decision also seemed to point out that the software used (Midjourney) was not something that was enough within the control of the person making the prompts to let the AI art be considered something that was done by a human... As in, the text prompts functioned more as "suggestions" and not as "orders", so that was not copyrightable.
However, if a different software was used for AI Art in a way that could reliably lead to the results you wanted, then it could maybe be allowed to receive copyright protection.
It was essentially something similar to how copyright of photographs work, where you can make the exact thing you want by pressing the camera button... If someone can make an AI art that does the exact thing they want, then it might be able to be copyrighted by pressing the "Generate" button in the same way a photo is copyrighted by pressing the camera's button.
At least that's the gist of what I got. The author of the work was apparently also experimenting with new AI generation techniques to see if they could get their work copyrighted if they used a different method to generate their images, but... Well, the articles I read about it were around March-April 2023 and I found nothing about how things worked out for this new work attempt (assuming it was finished, I dunno if it was).
So... Right now, it seems like the ruling is, "The standard methods of generating AI Art by themselves do not generate copyrightable art, but different methods might be ruled out differently."
That's the gist that I got from googling at least... Seems like it's still a complex situation rn.