No one person is to blame.
Mackay has to take blame for his dreadfully naïve summer signings, and lack of signing experienced PL players in vital positions. he also has to take blame for negative tactics in the away games against mid to low table teams.
OGS has to take blame for a dreadful January window. He also has to take fault for wrong tactics & team selections.
Tan's fault was not getting in someone with PL experience to assist/guide Mackay as soon as promotion was secured. He also erred in not sacking Mackay at same time as Moody. Then the vital error was in replacing him with an untried, inexperienced manager.
Nothing to do with the red shirts etc.
Ninian - these are valed opinions, however I disagree.
Mackay spent £35.0M or so - what would you expect for this investment? Champions League? Top Half? For £35.0M Mackay assembled a squad good enough to stay in the division, which for that amount of investment is a job well done. Had Mackay remained manager we would be safe by now (only an opinion I know). I agree he was a bit negative, but was starting to use Mutch & Noone after a half decent start.
OGS - no blame really - poor guy looked out of his depth from day 1 - CANNOT be allowed to stay for next year.
Tan - where to start - sacking Moody, sacking Mackay at the wrong time - should have stayed 'till end of season, threatening players with withdrawal of bonuses, booing his own players, having total disregard for Cardiff as a city, its fan base, its history, interference in team affairs, giving away Cornelius, when we were blatently short of fire power ( I know he wasn't exactly prolific but come on - 80 minutes playing time in total & Kenwynne Jones FFS).
Players - as I've said before - squad at begining of season were good enough to stay up & were actually playing well enough to stay up - in my opinion they weren't interested once Malcy's position was threatened -OGS's indecision & lack of tactical know how didn't help either. Can anyone explain why Caulker & Turner looked solid under Mackay, or Taylor actually looked good enough for Premier League, or Medel looked a bargain, or KTC looked an excellent purchase?