does anyone know why so many people left the final season? I know David Strickland committed suicide right before the end of the third year. But Judd Nelson and Andrea Bendewald both leaving first thing in season 4 sealed the shows fate.

One of the things that made SS a success IMO was that it was an ensemble show. Susan wasn't even one of my favorite characters on the series, but when Jack and Maddie both left, I felt like it gave the show a major blow. Losing David Strickland was enough for the show IMO. By season 4, only 3 of the 6 main characters were still there.