Most "Pitbull" news reports rely on the opinion of the officials in determining the actual breed. Local aggressive breed bans also use physical appearance as the deciding factor rather than DNA. There are probably a dozen plus different breeds that get lumped into "Pitbull" and if they were reported as their actual bloodline, we'd likely see a different picture presented. Staffordshire terrier, American Bulldog, Bull terrier, Staffordshire Bull, Dogo Argentino, plus lots of mastiff mixes.
If you cross a lab with a Shepard you can get a dog that some will see as a Pitbull.
The original purebred fighting dogs were also selected for their tolerance of being handled by lots of people. If they bit handlers they were culled out.
The irresponsible breeding happening in backyards can miss this aspect with any breed and create unstable dogs that don't like strangers especially if they're not socialized properly as pups. Add to this the powerful build of boxers, pits, worries rotts etc and it's a recipe for disaster.
A crazy, unstable poodle or beagle is more acceptable and forgivable because of its relative size. And for some reason pits end up in many cases with terrible owners who just want to breed them to sell pups for easy cash. The dogs take the blame for what people do.