The Serb left Vicarage Road in the summer of 2014/15 despite earning the club promotion to the Premier League.
"People called me crazy for leaving a team that had just been promoted," he said.
"They said it must have been a difficult decision for me to go that summer. But it was not. I didn't believe they felt I was the right person to take Watford into the Premier League, and they didn't make enough effort for me to stay.
"In this situation, my feeling was that it was better for me and for Watford too, to continue life. It wasn't complicated. As always, I went with my feeling. But I couldn't stay away from England for long."