The decline started when the Glazers bought the club, but they are not the sole reason we are in this mess.
I'm unsure if many football fans, or even all United fans, fully grasp the financial impact of the Glazer takeover.
United had zero debts and were a very profitable club with immense power in the transfer market by 2005. The Glazer takeover plunged the club into so much debt that between 2005 and 2010 we paid £75m every year in interest payments. I think again, sometimes it's difficult to grasp how much money that was then. This was 2005, Wayne Rooney, potentially the most exciting talent in World football, had just sold for £20m + £5m add-ons. Cristiano Ronaldo had just cost us £11m. Vidic and Evra cost us a combined £11m and Michael Carrick cost us £18m, all around this time. Just imagine what an extra £75m every year could have done for our squad.
Now, because we did have a fantastic squad full of proven winners and young talents like Wayne Rooney and Cristiano Ronaldo, we actually embarked on a very successful period on the pitch between 2005 and 2010, but we squeezed every last drop we could out of the team and squandered any advantage we had.
By the time SAF retired, the loans had been restructured but the squad was in urgent need of major surgery. In the 12-months between SAF retiring and LvG taking over, we lost Evra, Vidic, Ferdinand, Giggs and Scholes. Rooney was already regressing, RvP was in his 30s, Carrick and Fletcher both struggled on for another year but had their best years behind them. Park and Nani had also gone, and all of a sudden the squad began to look very short.
What compounded these problems was that because of our success we hadn't evolved as a football club. We had been so reliant on one man that there was no structure in-place to ensure continuity between managers. The scouting department was so bad Moyes was in shock at what he found. An accountant with no experience of being involved in football at any level was put in charge of overseeing the football side of the business. It was a recipe for disaster. We finally had some money to spend again but no idea how or where to spend it.
On top of all that, and a huge factor often missed by your average football fan, was the new multi-billion pound TV deal signed in 2013/14. Sure, this meant United had more cash, but it also meant our PL rivals were now richer and more financially stable than they had ever been. This made it all but impossible to sign players at a decent price from other English clubs. Times gone by, the majority of our big signings had come from English teams. Cole, Yorke, Sheringham, Carrick, Berbatov, Ferdinand, Keane, Pallister, Bruce, Irwin, Ince etc...
It was lazy but effective method of signing players. You knew roughly were you stood with these players as they were unlikely to have too many problems adapting. We also had the safety net, for a long time, of knowing we could afford to let the likes of Rio Ferdinand and Michael Carrick test their mettle at Leeds and Tottenham before signing them. It just isn't viable now. We should almost forget about signing players from the PL UNLESS there is some kind of contractual situation we can exploit. To quote SAF, there genuinely is "no value in the market" when it comes to English players, because our rivals have no motivation to sell.
So, plenty of issues, mainly stemming from Glazer debts/Glazernomics, poor continuity planning, failure to adapt to the changing landscape and having non-footballing people making decisions.
One of the reasons we never get anywhere is because we as a fanbase are still obsessed with managers, because we had one of the best of all time. We seem to fail to understand that the success of a Pep or a Klopp is only possible because of the world-class support they get from Begiristain or Edwards. We think that every new bloke who steps foot in the dugout will be the saviour, when in reality the ships captains are still headed directly at the iceberg and all our managers are really doing is rearranging the (vry overpriced) deckchairs.