They were bred, originally, as ratting dogs, which is why terriers were used when "creating" them but that doesn't mean their aggression is an innate behavioural drive like herding or tracking is. It comes from a fear response. The fear response is present in all mammals (fight, flight, or freeze).
If you lock a chihuahua in a pen with a bull it will either freeze or fight. The same would occur if you locked a rottweiler, springer spaniel, labradoodle, human, or hamster in with a wild bull. Clearly, some of these animals would have a better chance of surviving than others but the base response is still the same.
You can strengthen the chance of having an animal whose response would be to fight rather than freeze via selective breeding but that still does not change the fear response into a base behavioural drive. It is still a fear response.
Fighting breeds were selectively bred for their fight response and this historical breeding has resulted in the propensity for aggression toward other dogs but they were not typically bred for aggression towards humans. The opposite was true. The dogs needed to be handled while in a high state of arousal and so any dog who showed aggression to a person was not bred from as they weren't useful.
Not all fighting dogs will go on to develop dog-to-dog aggression, even dogs who have been used as fighting or bait dogs can go on to live happy, healthy lives in the right environment (Micheal Vick's dogs, for example)
That's not to say breeding for aggression may not have been an issue in more recent times and aggression can be bred into any animal with a fear response (see the silver fox study).
I'm not actually a fan of XL Bullies. I will happily admit there is something untoward going on with the breed. I don't think enough data exists for us to know for certain what that is. On the one hand, they have been responsible for a high number of attacks, on the other hand, all of the publicised attacks were a direct result of handler/owner negligence. Without in-depth research it is impossible to say these dogs are innately aggressive by breed alone.
My gut feeling is that they are the victim of the perfect storm. They gained sudden popularity during lockdown. The dogs who are maturing now didn't have the same opportunities for socialisation as dogs born before lockdown. They became popular with the wrong types of people who are not interested in breeding responsibly and who may well be breeding for aggression.
But the point is banning them is not going to change anything. Bull breeds are not inherently different, behaviourally, to any other breed. They have all the same base drives and the same fear responses as a labrador. What has happened to them as the result of poor breeding by unscrupulous people could happen with any breed.
We need to shift the focus to responsible breeding and ownership if we ever want to see a difference.