Thats only a small part of it.
SAF was responsible for not investing in the squad heavily enough in the two -three years before he left (and no RvP for a relatively cheap £24m was never going ot be enough).
For quite a few seasons its been evident that the midfield and defence needed some proper additions but nothing was done about it and the summer was even more of a disaster than was expected (but not wholly Moyes' fault).
I dont think anyone expected him to be the 2nd coming - but with a decent squad , **** , even just a couple of younger world class players Utd could well be a force again.
Its a bit of (lacking in) belief, luck and some tactics which are affecting the team the most.
Responsible for, or responsible for doing it? If he'd spent 30mil on a left back, that is 30mil less Moyes(or whoever else) would have had. Fergie did buy long term replacements for Vidic and Rio, Smalling and Jones were highly rated and wanted by many clubs. It's not Fergie's fault it turned out one is a sicknote and the other's gurning puts off his team mates. It was sensible to buy younger CB@s with a view to them being ready for the first team CB pairing as Rio/Vidic end up retiring/leaving, just unlucky neither have worked out. Evra is a more recently rubbish player(according to some/most) and probably while he realised he needed replacing it's not terrible to leave that choice up to the next manager.
Yes he could have spent this apparent 200mil warchest, but that would mean building a team of players to play in the style Fergie wanted, which may not suit the next managers style, or capability.
If you know you're leaving in a couple years it's prudent and actually sensible to save big purchases for the next manager to make his mark on the squad. Of course, what Fergie did was recommend an incompetent idiot for no apparent reason and so far he's been doing very bad business in the transfer market.
What Moyes could have done would be, buy a left back, and a proper winger, and a CB and that could have made a huge difference this season.
Evra for the first goal was doing everything you shouldn't do as a fullback, Vidic was out of place and had no need to rush out, both CM's were standing next to each other ball watching leaving a huge space behind them they were ignoring, but had Evra moved across into the gap like he should have done, particularly as he had a clear view of Sidwell making the run, he had every chance of stopping that goal being scored.
For the second goal, he didn't bother getting back. Had Evra done his job better today Utd may have won, and that could go for at least 2-3 other losses this year. So just replacing the left back could have made a huge difference, let alone CB's and CM's which the club is desperate for.
Mourinho came in and hasn't used Mata much then got rid, he wasn't suited to that team or the way it played. What if Fergie spent 200mil, and the players didn't suit Moyes, or Mourinho, or Ancelloti's style, and it's a lot of money wasted?