If they really wanted to win they never would have had Biden on the ticket. At a minimum they would have allowed a primary rather then forcing RFK out of the party and keeping any other potentials off the stage.

In my opinion Biden was clearly slipping 18-24 months ago. But even if that's wrong, the best way to show the country Biden was fit for another term and energize the party would have been putting him on stage to debate with other democratic leaders.