Conte managed Lukaku at Inter Milan, where the misfiring forward has returned on loan, a season after leaving for £97.5million.
The Italian said: "We are talking about a big amount of money for a player and I think we are talking about a really important striker in the world.
"But sometimes a situation outside of football happens and I think Romelu lived two years in Milan and he was the king. The fans showed him a lot of passion and I think he's a guy who needs this. And for this reason, I think he wanted to go back to Milan.
He added: "A lot of things can happen for the confidence to drop. Now it's right for him to play for an important club in Italy to try to get again confidence in himself."