Hardy was first attached to the film in 2013.
The British star was attached to the project in 2013, before Taron Egerton was eventually cast as the music icon in early 2018.
But Vaughn has now revealed why Hardy was ultimately replaced, explaining that the film was stuck in development hell when he came on board to help Elton and husband David Furnish.
“I said, ‘Look, I don’t understand how this hasn’t been made, and if you want me to team up with you, I’m in’,” the Kingsman director told The Hollywood Reporter. “I really think Tom Hardy is one of the best actors, but I felt he was too old for the role [Hardy is now 41].”
He continued: “And two, they said the idea was Tom was going to lip-sync.”
Instead, Vaughn suggested Egerton after he impressed as Eggsy in Kingsman. He also impressed with a rendition of ‘I’m Still Standing’ in Sing.
“John and Furnish were on the fence because they had Tom Hardy attached, but when they heard Taron sing, it was like a no-brainer,” Vaughn added. “They were like, ‘OK, he’s unbelievable’.”
Tom Hardy had originally signed on for the role of Sir Elton in 2013 but eventually pulled out after he struggled with the singing element of the film. “I’m not a singer. I have no idea really. I’m really trying because of Rocketman but it’s hard to open my mouth in that way,” he said at the time.
Last week, Egerton’s performance of ‘Rocketman’ was unveiled for the first time.
In April, Egerton also responded to criticism of his casting as Elton John. Some critics had questioned whether a heterosexual actor was the right choice to tell the story of the musician grappling with his sexual identity.