The Jays traded away 7 key pieces of the team i order to bolster their prospect pool and improve their salary situation in order to sign some big names this offseason. Most notably Yusei Kikuchi, Danny Jansen and Justin Turner were all moved to new teams.
AS you can see, Kikuchi, Jansen and Kiermaier are performing vastly better but it doesn't necessarily have anything to do with not being in Toronto anymore, sometimes a change of scenery is all it takes for a player to find his groove again.