On a totally unrelated subject. Last season Harry Kane was the captain of Tottenham and he scored a bunch of goals for the team. In summer he became a free agent and signed with Bayern for a cool E100M fee. Everybody thought that Tottenham was finished.
Not so fast. With Kane gone, other Tottenham players are scoring at a nice pace and the team is at the top of the Premier League. Moreover, they are playing well as a team, which is definitely the work of their manager. Of course, Tottenham got lucky in the controversial game with Liverpool, but hey in sports "they don't ask how you score; they ask how many." In the meantime, Kane is providing the much needed scoring for Bayern. Not much adjustment was needed for him to become productive for the team.
I can't remember any other case where the departure of the best player improved both his former and the current teams.