WrestleMania is not just a wrestling show. It's a whole lot more than that. WrestleMania is a spectacle, the true embodiment of the sports entertainment vision of Vince McMahon. At 'Mania, entrances, video packages and even mini Kid Rock concerts can get more time than the actual wrestling.
A big part of what makes WrestleMania special is the extravagant sets, the fireworks, the lighting and so on. These are the things that help to distinguish it from the typical WWE PPV and help it to retain its aura. WWE spends A LOT more money on WrestleMania than it does on any other event of the year.
WWE superstars do their bit, too, by getting special ring gear made for it. The WrestleMania gear usually has something that distinguishes it from the wrestler's usual attire, whether it be a different colour or have a pop-culture theme or even something completely different to what they usually wear. You usually wear trunks? Well, it's WrestleMania, so why not wear a singlet?
WrestleMania gear is more often than not only worn the one time. This is a special occasion, after all, and every time that the outfit is worn it makes it somewhat less special. Before this year's 'Mania you can bet that the superstars and divas will call their tailors and seamstresses and ask them to make them 'something cool' for the show.
Everybody wants to look cool at WrestleMania. Perhaps they can check out these guys for inspiration.