The biggest factor IMO is something no one mentioned yet: we can only see one face of each step (either the top or the wall). If a photo is taken from the bottom, we would almost always be able to see the tops of the first few steps, which isn’t visible here. If a photo is taken from the top, the walls would pretty much never be visible (if they were, you could also see the photographer’s feet).

It is possible that this is an extremely long flight of stairs or that the photo was taken from a deliberately deceptive angle, but if that’s the case I have to say it was expertly done, because I am CERTAIN that we are looking from the top and the mattress is at the bottom.