One big question I see is the assumption that because something is of Russian origin, they had to know. They sell this equipment on the open market and they are the major supplier of arms to Syria. Just because a Russian Drone was flying over the site doesn't mean it was doing so under the command or authority of Russia itself. Same with the jet that destroyed the hospital.
Hell, the ISIS groups there are using Russian arms as well, many taken from Syrian bases and warehouses they over-ran.