Aguero, 23, scored a hat-trick in the 3-0 defeat of Wigan Athletic on Saturday to take his tally to six goals in four games, having joined City from Atletico Madrid in July for an estimated 45 million euros.
"I said Aguero needed a team that would support him, so that Aguero can play in the Champions League, can play in very important championships," Maradona told a news conference in Dubai on Sunday ahead of his first competitive game in charge of the city's Al Wasl F.C.
"It was not the case with Atletico Madrid. People from Atletico Madrid said I was a fool. I told them that foolish person wasn't me, because Aguero is now playing for a team - Manchester City - that will fight for everything. Now Aguero is playing in a place that he deserves."
City have won all four league games this season and are second only to local rivals Manchester United on goal difference.
Maradona, who managed his nation at last year's World Cup, also found time to slam the Argentina Football Association.
"Football there is like a museum - the youngest person is 95-years-old," he said. "Stay at home with your grandchildren and allow young people to manage Argentinean football."
He played down expectations he could lead Al Wasl to the United Arab Emirates league title at the first attempt.
In a city used to bombastic promises, Maradona would not predict how his team would fare with Al Wasl opening the season in a cup tie against league champions Al Jazira of Abu Dhabi on Thursday.
"We will be very careful against a team that we know a lot about," Maradona said.
"They [Al Jazira] have the advantage that they have been playing together for longer than us. We have our tactics so can hurt them. We are not going to be totally defensive."
Al Wasl finished a distant sixth, 22 points behind Al Jazira last term in the 12-team Etisalat Pro-League.
Maradona will be hoping new signings Uruguay's Juan Olivera and former Bari midfielder Mariano Donda can help them qualify for the Asian Champions League.
"We are not talking about being champions, we are talking about going step by step, improving day by day," said the World Cup winner.
The ever colourful Maradona also warned he would try to protect his players from any rough tactics.
"I want everyone to treat me with respect. I am not a violent person, but if they want to have an issue with me... If you try to put a finger in my eye, I will put two fingers in your eyes," he said.
"If you play tough, if you injure my players, I will complain. I will jump. This is how I am made and this is how I will die."
Ghana's Asamoah Gyan joined Al Ain on loan from English Premier League outfit Sunderland on Saturday to become the latest high-profile player in the UAE league but Maradona thinks the UAE national side will continue to struggle.
"It is tough for them - after seeing them play, you don't feel confident," he said. "I think that UAE ... is a team that has to improve a lot if they want to
