In a new PEOPLE cover story, the Oscar winner and ‘Horizon’ director looks back

— and ahead — at his life and iconic 40-year career

His affection for the series and cast is one reason controversy around his exit was especially hurtful to the star,

who played patriarch John Dutton III for five seasons, from 2018 to 2022. He bristles at reports he left because of Horizon: An American Saga, his ambitious western epic whose first chapter hits screens on June 28, or that he offered just one week of his time.

In fact, Costner had long front-burned Yellowstone after initially signing on for just one season.

“When it was first pitched to me by Taylor [Sheridan] it was one season and [like] a long movie, which [is] speaking my language… but ultimately, I think what happened was the studio didn’t want that,” he says. “And because he’s such a prolific writer, he said, ‘I can do that. I can make a series that goes on’.”

In fact, he was game to continue, but there was no timeline or new material, he says. “There was a moment where that show for me stopped for 14 months… That’s the fact. I could have done a lot of things in that time, but I wasn’t aware that that [hold-up] was going to happen.”

As is his way, Costner stayed mum and rode out the rumor-filled churn but was “disappointed” no one came to his defense. “I read all the stories,” he says. “I was disappointed that nobody on their side… ever stepped up to defend what it was I actually did for them. There came a moment where I thought, ‘Wow, when is somebody going to say something about what I have done versus what I haven’t done?’”

Costner was drawn to the project when it first came his way and was excited to collaborate with Sheridan. “I liked the writing and really, really liked what Taylor was doing,” he says. “He understood the world of modern-day ranching and was able to create all this other type of drama inside it, but in an effective way.”If the script and scenario was right, Costner notes, he’d be open to returning. “I’ve always felt that…It might be an interesting moment to come back and finish the mythology of this modern-day family,” he says. “And if that happens, I would step into it if I agreed with how it was being done.”