The Belgium striker joined United from Everton for £75 million ($98 million) in July 2017, scoring 42 goals in his two seasons at the club before moving to Inter in August last year.
He has been in superb form for Antonio Conte’s side, scoring 18 goals to help the club sustain a challenge for the Serie A title.
Those performances, and United’s reported interest in signing a striker this month after Marcus Rashford’s back injury, have raised questions as to the wisdom of allowing Lukaku to leave Old Trafford.
But, in an interview with Sky Sports News, the 26-year-old said the decision was his and it had worked out well for United as well.
“I think I had to re-find myself,” he said. “Last year was difficult for me on the professional side because stuff was not going how I wanted and I was not performing as well… and I just came to the conclusion that it was time for me to change environment.
“I made my decision around March, and I went to the manager’s office (Ole Gunnar Solskjaer) and I told him it was time for me to find something else.”
“I think I made the right decision and I think Manchester United now has made space for the younger players to come through so I think it was a bit of a win-win situation for both of us,” he added.
The Belgian was signed for United by Jose Mourinho and had an excellent first season, scoring 27 goals as United finished second in the Premier League.
But Mourinho was sacked in December 2018 after a disappointing start to the season, with Lukaku also unable to discover his best form.
Former Chelsea manager Conte has managed to bring the best out of Lukaku this season, pairing him with Argentine forward Lautaro Martinez to lethal effect.
Lukaku said the Italian knew how to extract the most from his whole squad but revealed he was not afraid to get tough with the players.
“The manager, he tells it straight to your face if you’re doing well or wrong,” he said.
“You work hard, you train hard and you play,” he added. “If you don’t do what he says, you don’t play. You know where you stand — and that’s what I respect about him.”
