Looking back, Ronda Rousey was done in the UFC when Holly Holm knocked her out at UFC 193. That was 15 November 2015 and in two rounds Rousey went from a whirl of fury and fire who stomped across all-comers to a crushed soul.

It happens this way in fighting, especially in MMA. Once a great champion has been vanquished, it’s hard for them to stand back up. There was a recovery, a promise of future dominance wrapped in virulent torrents of insult and agitation. But when Rousey finally fought again, on the penultimate day of 2016, the lioness was gone. She took a 48-second pounding from Amanda Nunes and stepped out the gate for good.

Her separation from the UFC was made complete on Sunday night when she announced a new life in the WWE. The move was hardly a surprise, she had long been rumored to be joining the organization and had teased such a transition several months ago. But there too was a sense of finality in her decision, a complete break from the fighting circuit that made her name and for whom she may have made billions.

Ronda Rousey and the UFC were good for each other, delivering express elevator rides to mainstream acceptance. Without Dana White and the pay-per-view extravaganzas, she was just another ex-Olympic judo medalist looking for a paying gig. Without Rousey, the UFC never would have exploded onto newspaper sports pages, magazine covers and to the tops of general interest media sites.

Rousey made millions in her eight UFC fights, then earned even more as a celebrity who crushed other women in the octagon and charmed outside it. She gained nine acting credits including a co-starring role in the Expendables 3 and became an empowering voice for women with her crusades against domestic violence. She turned into a legitimate Hollywood star.

But Rousey presence took the UFC to Hollywood too, making their pay-per-views must-buy television. The more famous she became the bigger the UFC got. While Conor McGregor is the UFC’s biggest name, Rousey will always be the UFC’s first mainstream superstar. She is perhaps their biggest star ever.

Without Rousey the UFC would never have had female athletes. Before 2012 White famously insisted he did not want to promote women fighters. But after watching Rousey tear through Strikeforce to become that organization’s champion in under two years, he changed his mind. White had never thought there were enough females to fill a UFC women’s division and yet Rousey was so determined, so engaging, he decide to create one.

“I’m telling you, this girl, she’s nasty,” White told The Jim Rome Show when he announced Rousey’s signing in 2012. “She might be beautiful on the outside, she’s a Diaz brother on the inside. She’s a real fighter and she’s very talented. She has the credentials, the pedigree, everything. And she has the it factor. I think she’s going to be a big superstar.”

Then she was. Her second UFC fight, a third-round submission of Miesha Tate at UFC 168, sold more than 1 million pay-per-views – though the main fight that night was Chris Weidman-Anderson Silva. She soon became her own headliner, supplanting the males who made up the UFC establishment. After Tate, her fights were something to behold – a frenzy of fists, kicks and takedowns that all ended in the first round.

By the time the Holm fight came alone, she had made a mockery of the women’s division White was trying to create. She was the biggest female in fighting and undoubtedly helped drive up the value of the UFC before its $4bn sale to WME-IMG in the summer of 2016. Then it was over. A swirl of Holm punches knocked from her all air of dominance. Her comeback against Nunes almost seemed misguided given the beating she took.

But those defeats might have been the best thing to happen to women in the UFC. Her arrival gave them a chance. Her fame gave them their own spotlight. But her vulnerability opened a door. Since the Holm loss in UFC 193, women have headlined five main UFC pay-per-view events, including Tate and Nunes in White’s July 2016 showpiece, UFC 200. She made possible the power of women like Nunes, Joanna Jedrzejczyk and Cris Cyborg – who might well be the next Rousey. She may have gone to wrestling but she changed the UFC for the better.

“I’m very happy for her,” White told the Las Vegas Review-Journal’s Adam Hill, after her move to the WWE became official on Sunday. “She loves pro wrestling and has always been a big fan so I know how much this means for her. She keeps accomplishing everything she’s ever wanted.”

In the end, her UFC time was brief, barely four years long. She used the organization to become bigger than life just as the UFC used her to climb into the mainstream. It became the perfect marriage of convenience.