Bobby is the coach/quarterback because he is the only rock star on the team. If Boz Scaggs had shown up, Bobby would still be the QB, but Boz would have play-calling duties. That’s how being a rock star works.
This third championship was particularly sweet; the year had a rough start, as the team sought to institute a West Coast Offense and Bobby kept showing up three hours late.
You might also note that Bobby is putting more effort into this flag football game than he did into his entire solo career.
Phil was thrown off the team because he wouldn’t stop doing that thing where you loop the flag around the belt so no one can get you down.