As a photography geek I must say those are incredibly good photographs! Is there some kind of trick in play or was the art of photography really that good back then?
Besides the large plates, I think you're reacting to the focus as well. We've gotten very used to our small lenses and their infinite depth of field that keeps everything focused. We're so used to it that now it's a feature to have a smartphone camera that can blur the background. But those old cameras did that automatically, because they were only capable of a narrow depth of field and the photographer had to be really careful about where the focus was when he composed the shot.
I believe the photographic plates of the day would have been large, maybe 8x10 inches and developed or printed at 1:1 scale.
That would give a pretty good head start on quality.
It is easy to forget just how good film or plate photography is. I scanned some slides from the 80s and they were amazing, easily printed at A4