The playmaker appeared settled at Goodison Park, but only had a year left on his contract.
With contract talks not progressing, the club decided that selling him was the best course of action.
The Fulham midfielder told The Athletic: "It wasn't an easy decision [to leave]. I enjoyed my time there.
“Especially the last couple of years. I felt like they [Everton fans] warmed to me.
"At the same time, I felt I needed a new challenge, and Fulham are giving me the platform to express myself and do that."