The Scot was sacked in April, not even getting the chance to see out a full season in charge as Sir Alex Ferguson's replacement as United made a shocking defence of their Premier League title.
It left United officials - Ferguson included - red-faced after Moyes had been installed as 'the chosen one', with the former Everton boss becoming 'the sacked one' before the season was out, at a club famed for giving managers time.
Moyes was accused of bungling in the transfer market but claims he tried to sign Cesc Fabregas, Cristiano Ronaldo and Gareth Bale, although ultimately he did not and was judged on his results.
Louis van Gaal has since moved into the dugout at Old Trafford and Moyes is now ready to return to management, but insists he was not given the time needed to get to grips with one of world football's most high-profile jobs.
Speaking to the Mail on Sunday he said: "It was a step into the unknown and, looking back now, it was near enough the impossible job."
"But it was the right job for me. I'd been at Everton for more than 11 years. We'd qualified for the Champions League, got to an FA Cup final, I'd been voted manager of the season three times. I was among the most experienced managers in the Premier League. United had always had British managers.
"I was devastated to lose the job because it was something I felt I could make a real success of. We knew it was going to take time to make the necessary changes. It was going to take time to evolve. But we were in the process of making other important changes. In the end, I don't feel I was given time to succeed or fail."
The failure to significantly improve the squad Ferguson left him also hindered Moyes who, along with chief executive Ed Woodward - also new to the role - missed out on a number of targets.
"It's been well documented that we wanted Fabregas, Bale and Ronaldo. There was talk of Ronaldo when I first arrived. We were close to getting a couple of major names," he said.
"I'm not getting in a blame game here but things just didn't materialise. I had taken over from the most successful manager in history. The chief executive had taken over from one of the most renowned administrators in the game [David Gill]. So it was a new job for two people."
Moyes was shown the door on April 22, but the story of his demise had become public knowledge the day before.
The former Celtic defender, knowing his time was up, admits he arrived at United's training ground even earlier than usual at 4am in readiness for his sacking.
"In the end it was difficult for my family, the way we discovered - via the media - that I'd lost my job," he said. "We have always tried to do things the correct way. I know it comes with the territory, and I know if you lose matches you risk being sacked. But how it affected my family made it hard. "
Much was made of the manner of Moyes' departure and that no reference was made to his players - with whom he was reported to have had difficulties with - in his leaving statement.
"On the day I lost my job I spoke to every player at the training ground," he said. "I called the players into the dressing room at 10am that morning and told them how disappointed I was."
The presence of Ferguson looming in the stands was given plenty of headlines as Moyes toiled on the touchline, with the club's most successful ever boss often seen glum-faced as his predecessor laboured.
Moyes, though, insists he always had his compatriot's backing.
"I've met Alex on several occasions since I left," he added. "And I spoke to him about the days surrounding my departure. He explained it to me and I totally accepted what he said. He was in a difficult position, and I understood that.
"At no time did I ever have anything other than 100 per cent support from him. He was always incredibly good to me. We had several meetings over the course of my time at the club. We spoke regularly. And I saw him being around me only as a positive."