They established early on in the movie that wrestling is "fake" (or pre-determined, or whatever they called it). Yet at the end when Paige is wrestling at the WWE, everyone's on the edge of their seats as if it's a real match without a pre-determined winner.
At the end of a wrestling match, the victor does celebrate like they've won a match. That's how wrestling works. What did you expect her to do? Get the title, and just silently leave the ring?
Everybody knows that wrestling is a pre-determined entertainment show, rather than legitimate sporting contest. But in each match the show lasts from when the wrestlers walk down the aisle to when they return back up and leave the crowd behind. They don't break character at all. So any wrestler winning a match or title acts that way.
Besides, it doesn't mean that there is no real emotion in wrestling. In the movie Paige hadn't known she was going to win the title until shortly before the match. After everything she'd gone through to then be at Wrestlemania, the biggest event of the year, being able to lift a WWF title in front of thousands of fans. It's not hard to imagine that part of the celebration was legitimate.
The entire scene was shot to make it look like she was an underdog, still trying to prove herself, and that she was celebrating at the end because she proved herself.
She was insecure of herself in the locker room. She was shown as nervous and freezing when picking up the mic, and that everyone was "nervous" for her, even her family and the WWE manager guy.
But that is not the case. From the moment she entered the ring, she already knew she "already proved herself", because she had already been told she would win.
I understand the part of the show, it's acting, of course. But they also used that to make us feel like a sport turnaround underdog winning, instead of an actress performing her role perfectly.
Her being nervous and freezing up on the mic wasn't to make her look like an underdog, just that she was nervous when finally on the big stage. She'd previously been used to wrestling independents in small halls. Suddenly she's at Wrestlemania at an NFL ground. Tens of thousands of pairs of eyes were on her. Also bear in mind, when she froze her opponent clocked that she was nervous and took to the mic again to buy her some time and to try and provoke a reaction. Rather than acting as if wrestling was a legitimate sporting contest, if anything that hinted at the worked nature of pro-wrestling. The one wrestler with the big-venue experience helped her more through the nerves of her first big time mic-session.
The worried look of her trainers or The Rock watching on weren't because they were nervous that she wouldn't win. They were worried that they'd misplaced their faith in putting her out there, because they could tell she was too nervous to talk.
Thinking about it, in your defence, when I first watched it and the family were getting into it my first thought was; "Did she not tell them she was about to win? Guess not."
That's the problem with wrestling movies. They can't determine whether or not it's kayfabe throughout the picture. The only movie that did a good job of it was Body Slam ... and that movie sucked.
Do you know what its like to be a wrestling fan? Even if you can predict who will win or are told who will win you can still find the matches exciting. Now imagine you're a "wrestling family" and watching your 18 year old daughter make it to the WWE to have their match on Monday Night Raw the night after Wrestlemania. That would be THRILLING! Even if they know who will win. Its also a sport where people have been paralyzed or severely injured. So you're hoping the match goes just as you'd dream it. I took it as they weren't told who would win but either way those emotions would still be genuine.