This feels most likely. From his retirement fax and the scene with his sons in the documentary, it feels pretty clear that the state of the franchise, the exodus of his teammates, the coaching style of Bobby Ross, and the unlikelihood the Lions would be much better anytime soon just sapped that passion.
If you take away the chances to win, to collectively complete with people you enjoy, and then you're someone who doesn't care about accolades... What was left for Barry to play for?
As a teenager, it was certainly shocking, sad, and confusing. As someone now older than Barry was when he retired, I understand the investment he needed to put in want matched by the remaining passion he had to play
Oh so you're stealing my childhood dreams. No, that's fine. Totally cool. Barry and Herman Moore...