Rooney found the net in England's World Cup wins over Montenegro and Poland over the past week to guide Roy Hodgson's men into the World Cup finals.
It follows on from his outstanding efforts for United with Rooney, 28 on October 28, having scored five times in his last six games.
"I saw him like this on the first day of pre-season yet I had to keep telling everyone that was the case because the media thought it was different," said Moyes.
"I saw him in great form. He was in great fettle. His training was fantastic from day one.
"But people kept saying different things and I found it difficult to prove it different.
"You can see by his form and the goals he is scoring that what I was saying was right."
As Moyes acknowledged, Rooney is now approaching a point in his career when he is expected to handle more responsibility.
And he is pleased to note the former Everton star is doing exactly that.
"He is at an age where he would be one of the main players," said Moyes.
"He is certainly a main player for Manchester United and he is one of the main players for England.
"That is what we expected.
"He takes the responsibility, scores the goals when it is required. He has done that from a young age.
"But the age he is at now he has that maturity which shows in how he plays, the condition he is in and the way he is playing for both club and country."
Source: PA
Source: PA