Season 1s are great, setup, some payoff, a bit of lead into the overarching story. Then season 2 to X. The heroes win and then lose in the final episode, cliffhanger to next season. People get bored. Final season is announced and they wrap up the show.
P&R continues to be in my mind what happens when you let a show with talented actors and smart writers marinate a bit. Everyone on the show became a bigger star/household name afterwards.
So many shows get cancelled after a season. And I wonder how many shows, if they got that P&R treatment, would be amazing today.