The absurd postmodern sitcom created by Harmon has always struggled with low ratings, but has garnered a devoted following and critical acclaim. While its numbers are bad, they're not bad for NBC, who can't seem to find a hit with both hands and a flashlight.
Harmon created the show, and was the driving creative influence. After the third season, he was fired by Sony, who cited his continual lateness delivering scripts, amongst other creative differences. He had a public and ugly feud with cast member Chevy Chase (Chase himself left the show mid way through the fourth season) and according to Harmon, Sony never even fired him in person (he was told via an executive producer on Community that he was done).
A 13 episode fourth season was greenlit and shot, with David Guarascio and Moses Port as producers. Many long time fans of the show (including this writer) felt that fourth season was nowhere near as strong as the previous three.