Because their owners took the parachute payments out of the club. http://www.theguardian.com/sport/david-conn-inside-sport-blog/2012/mar/06/blackpool-karl-oyston-players-wages
Certainly later than any last season. Perseus also started the thread for the game v Sheff Weds where we would have probably assumed we should win, but some were worried whether we were good enough.
I think if we were to lose today, I would probably laugh at the idea of the anger it would cause.