EXCLUSIVE: The Real Reason Olivia Newton-John Broke John Travolta's Heart Revealed Nearly 48 Years on From Their Romance

Olivia Newton-John was the one John Travolta wanted, RadarOnline.com can reveal. After finding success on Welcome Back Kotter, the actor – whose breakthrough movie, Saturday Night Fever, was months away from release – leveraged his newly found fame to get the beautiful blonde an audition for 1978's Grease.

"I never let up on it," said the 72-year-old. "I insisted that she be met, and that we cast her."

His instincts couldn't have been more spot-on. The pair's undeniable chemistry as Sandy Olsson and Danny Zuko became the backbone of one of the most beloved movie musicals of all time, raking in $366 million worldwide at the box office. But the connection transcended the screen. "For John, it was instant attraction with Olivia," shared an insider. "He fell for her."

Now, the costars got so close that the late singer-actress considered tying the knot with Travolta – before ultimately breaking his heart and turning down his proposal. At issue? His religion. Two years before he and Newton-John filmed in the summer of 1977, Travolta converted from Catholicism to Scientology.

Though it was a dealbreaker for Newton-John, she seemingly continued to struggle with her decision. According to a new tell-all, the Physical songstress approached a bandmate about the predicament more than two decades later.

A Little More Love: The Life and Legacy of Olivia Newton-John, by Matthew Hild, claims she opened up to her musician pal, knowing he'd previously been wed to a Scientology member himself.

"Obviously, you know John is a Scientist," she allegedly said. "I know the Church of Scientology really reveres him as a very valuable follower. If I had married John, would he have expected me to become a Scientist?"

Her friend responded that it wouldn't have been "mandatory," but "encouraged" – evidently confirming Newton-John's long-ago fears. "Thank you," she supposedly replied. "That's all I want to know."

Until her death at age 73 in August 2022, the Xanadu star was left to wonder what could have been. As she recalled in her 2019 memoir, sparks flew right away on set. "When we walked inside the room together, it was magic, and everyone saw it," Newton-John wrote. "Yes, we really liked each other and there was an attraction."

While the twosome often played into rumors of a real-life romance – even sharing a steamy smooch at the official after-party following the premiere of Grease – they long denied dating, insisting they were each involved with other people during filming. However, their costars, including Didi Conn, were left unconvinced.

The actress, who portrayed Frenchy in the hit flick, recalls John being very into Newton-John. As Conn tells it, the leading man pulled his counterpart in for the "juiciest kiss" in one cut scene – and Newton-John wasn't mad about it.

"You see for a moment she's surprised, and then she responds. It's juicy, and it's great," said Conn, 74.

"They weren't acting in that moment. It was like he had his chance and he was going to take it. It was real – it really was." (Director Randal Kleiser toyed with the idea of having the pair kiss one more time – in the last scene of the movie when their car goes airborne – but ultimately decided against it.)

Newton-John had always been Travolta's dream girl. "If you were a young man in the '70s, and I'm sure many of you were out there, if you remember that album cover of Olivia with that blue shirt on, with those big blue eyes staring right at you, every boy's, every man's dream was, 'Oh, I'd love for that girl to be my girlfriend,'" he gushed.

Her appeal extended far beyond looks once the castmates met in person. "John became enamored with Olivia," said the insider. "She was an older woman, five years his senior. He knew she was the kind of woman who would tell it to him straight; there was nothing pretentious about her. She was also warm and caring, and she had a captivating voice."

Despite getting rejected on a romantic level, Travolta remained hopelessly devoted to his leading lady. The duo maintained a tight friendship over 45 years and reunited professionally on more than one occasion.

Aside from costarring in 1983's Two of a Kind, they recorded a holiday album, 2012's This Christmas. "There's a safety I feel when I'm with him," raved Olivia. "He's always been my protector."

The bond worked both ways, insists the insider: "She was a constant support throughout all his highs and lows, and he was a devoted friend during her battle with cancer."

When she finally succumbed to the breast cancer that had tormented her for 30 years, Travolta was devastated – even more so because wife Kelly Preston had died from the same disease in 2020 at age 57.

"My dearest Olivia, you made all of our lives so much better," he wrote on social media. "Your impact was incredible. I love you so much. We will see you down the road and we will all be together again. Yours from the moment I saw you and forever! Your Danny, your John!"

Almost four years later, Newton-John remains on his mind. "He loved her so much," said the insider. "Not a day goes by that he doesn't think about her."

The second famous blonde to dance her way into Travolta's heart? Princess Diana. In 1985, the Urban Cowboy star took the People's Princess into his arms and twirled her around for 15 memorable minutes at a White House gala, later describing the moment as unfolding "like a dream."

The occasion was a celebrity-filled state dinner, hosted by President Ronald Reagan and First Lady Nancy Reagan. Per Travolta, Mrs. Reagan discreetly told him that Conn wanted to dance with him, but he would need to take the lead.