It hasn't really "all" gone wrong though has it ? Twice champions, once runners up, FA Cup and League Cup winners and FA Cup finalists in the last 4 years.
If we're talking about this season since the turn of the year, in my view, what we're seeing is the inevitable result of FFP. After we won the league for the first time we were hamstrung in who we could sign without having had time to establish an infrastructure to identify young and cheaper talent. We were held to ransom over transfer fees as everyone knew we a) had to buy and quick, b) had to buy English and c) appeared to have pots of money. That's how we ended up with Rodwell and Sinclair, not through any ill-will towards Mancini.
Since then, it has been a matter of trying to balance the squad whilst being out of the market for the top players but held to ransom for the middling players. Fernando and Mangala may come good but 5 or 6 teams seriously challenging for the top 4 is unusual and there is no time for them to acclimatize.
At the same time, the relentless negative publicity and UEFA's implication that we have, somehow, cheated has permeated through to the club. Imagine being a Spanish player coming to England and getting zero credit for winning the league, simply an unprecedented financial penalty and restrictions on transfer fees, wages, sponsorship deals. And don't tell me that this doesn't affect the players, Vinnie commented on FFP only this week. They know it has been put in place to stop us. It won't, but, in my view it will have to be a longer term project and that will be a lot healthier than doing what we had to do.
We may fall out of the Champions League this season but that does not have the finality some people like to torment themselves with.