The Frenchman had been one of the key reasons why Hulkenberg opted to leave Force India at the end of last season and move to the French manufacturer for 2017.
"This was the hardest part of my decision, because I am close to Nico and I put a lot of efforts in getting him drive for Renault," Vasseur told Canal+ Sport.
"Nico and I talked a lot about my decision. He's been very supportive. My decision was hard for him to accept, but he is fully involved and he will give his best.
"The team is being restructured and for me it was important to have a leader," Vasseur added. "Whatever may happen, Nico will act as a leader and pull the team forward. I think it's a crucial factor in the success of a team.
"That's a reason why I wanted him in the team," he said. "I think he's one of the most talented drivers I've seen in the junior series for the past 10 years.
"Only three drivers captured the GP2 title in their rookie season: Lewis Hamilton, Nico Rosberg and Nico Hulkenberg. I think Nico is one of the few drivers who can win the world championship."
As for his own future plans, Vasseur said that he continued to follow Formula E and would still be running the ART GP2 team.
"As far as Formula One is concerned, we'll see what the future holds."