Kevin Costner's departure and interference led to Yellowstone's failure. He abandoned the show for a film project, causing scheduling conflicts. Costner's creative demands clashed with the writer's vision, causing production issues. His personal life, including divorce, further disrupted filming. Despite damaging the show, Costner refuses to return for final scenes unless they meet his satisfaction, jeopardizing the series' conclusion. Ultimately, Costner's actions are blamed for Yellowstone's downfall.