The Red Devils were completely outclassed by Brendan Rodgers' men at home to be condemned to their ninth loss of the campaign and Moyes was struggling to work out why things had been so difficult for the club this season.
Steven Gerrard scored twice from the penalty spot before missing a third when Nemanja Vidic was sent off after receiving a second yellow when he fouled Daniel Sturridge but Moyes did not have too much to say about the decisions against his side.
"We didn't play well, Liverpool deserved their victory," said Moyes after the loss.
"Some decisions were correct, some were incorrect but overall I'm disappointed.
"It is difficult to explain it."
He added: "We have to play better and make ourselves harder to beat, harder to play against and we are also going to have to make sure we are creating and taking more opportunities.
"We have a lot to do to do both those things. I think the job was always going to be hard. Yes, it is harder (than I thought) I would say so."
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