Pitbulls are not the only dog breed used for fighting. Actually, it's common for even Pug's and Pomeramians to be used for dog-fighting, but it's usually overlooked under the media hype that Pitbulls are the only ones used, when that's not true(I think this is only in other countries, but did you know there are major horse-fighting rings as well?)
I will note that Pitbulls were bred not for years but centuries as War dogs(or at least their predecessor breeds were), during more medieval times and even earlier than that when war was a prevelant and common event, as well as many other pit-bull-like and bull-dog-like breeds. Same with Mastiffs. Some are prone to genetically be more aggressive, as is the case with many of the breeds people mentioned before(especially concerning Dobermans), but can be taught out with very careful handling.
Akita were actually bred more as hunting dogs than fighting dogs at first(at least the Japanese variety; there is a different between an American Akita and an Akita Inu, both in size, coloration, and sometimes temperament) but it wasn't unusual for them to be alternatively used for fighting dogs as well, because initially they were bred to hunt bears.
Tosa Ken are still used for fighting in Japan today in some areas as a legal sport, but to my knowledge the criteria for a "Tosa dog fighting ring" is far different from the American illegal gang fighting ring standards.
Dog fighting in American gangs can have a single match last for an hour or more, until one of the dogs is killed or too wounded to fight back or move. Tosa dog fights in Japan have time limits and end immediately when one of the dogs barks, yelps, or cowers out of the fight, or if the owner throws in the towl, or the on-site vet declares an end or that it's too dangerous. I wouldn't call it "humane" or "sofisticated", neccessarily, but they aren't as horribly brutal and actually have set rules and standards to what they'll allow as an official thing. I've seen a lot of the videos of the dogs during or after the fight and often the dogs barely even have scratches on them, and never mauling or any horrible goring like we see here with illegal fighting ring dogs. And really, they're more like sumo wrestling matches than claw-and-tooth fights like with pitbulls and other breeds that are fought.
One such video of presenting the champion dog AFTER the fighting matches finished.Dog fighting evolved in Kōchi to a form that is called tōken (闘犬?). Under modern rules, dogs fight in a fenced ring until one of the dogs barks, yelps, or loses the will to fight. Owners are allowed to throw in the towel, and matches are stopped if a doctor judges it is too dangerous. Draws usually occur when both dogs will not fight or both dogs fight until the time limit. There are various other rules, including one that specifies that a dog will lose if it attempts to copulate. Champion dogs are called yokozuna, as in sumo. Dog fighting is not banned at a nationwide level, but the prefectures of Tokyo, Kanagawa, Fukui, Ishikawa, Toyama and Hokkaidō all ban the practice.[22] Currently, most fighting dogs in Japan are of the Tosa breed which is native to Kōchi.
The costume she put on the dog afterwards is also basically a ceremonial award for the champion dog to wear, to show he's a champion.
They're listed under the "Dangerous dog breeds" acts as well because they're a mastiff-originated breed. It seems there's sort of a stigma that dog breed with certain histories and physical appearance are "dangerous" by default. Kind of sad really.