I just don’t see how he got from that image to that caption. Anyway, the title translates as “Behind the Curtains”, so I suppose the artist was trying to be profound as artists have a habit of doing. Anyway, the picture is at the Gemäldegalerie Dresden, where it has been for over a century. See https://skd-online-collection.skd.museum/Details/Index/246526 for their page on this work. It’s sparse and in German, but at least it’s there at the painting’s own happy home.
On the circus in art, there’s an interesting page at https://eclecticlight.co/2019/04/21/circus-performers/ that places this picture into a useful larger context. Worth reading.
Since the Wikipedia article on Knaus is a straight lift from the 1902 New International Encyclopdia, you might as well go straight to the source at https://books.google.com/books?id=jl3BbMARd-sC&pg=PA291&lpg=PA291 and read it there if you’re using a decent size screen—not a phone or tablet.