It’s human psychology.
Something you used to have is no longer yours, but you want to keep up with it. Many people still follow their exes on social media to see how they’re doing. When people put pets up for adoption, it isn’t out of the realm of possibility they check in on how they’re doing.
It’s the same thing in sports fandom. If things end amicably with a fan-favorite player leaving the team, the fans will naturally keep up with how they do. If you have a college team, you’ll be fans of said players and root for their success in the big leagues.