> Why would anyone think that was "subject to copyright"?

Because it is subject to copyright in some countries. In France, for example, photographs of certain buildings cannot be published without the permission of the rights owner.

But it’s the building owner who would have the copyright, not whoever was the first person to have it somewhere in the background of a picture

The question was whether a scene can be subject to copyright and I answered that question. Whoever downvoted it probably doesn't get basic aspects of photography

If I am the photographer and I set up decorations, lights etc. then the scene itself is my creative work. The other guy will have trouble claiming any copyright over his photo of the same scene because it is based on my creative work.

Not in this case because the scene is naturally occurring. So we can move on to other things that make the final photo like sensor capture and processing

> What do you mean by "scene"?

Photons mostly

> Why would anyone think that was "subject to copyright"?

Scene itself is absolutely ""subject to copyright"" in many cases, like when it's set up by photographer or includes recognizable people (they can sue you if you sell a street shot with their face)