What sport were they bred for? Bull baiting? Dog fighting?
The line of dogs that led to the development of the premier pit fighting breed goes way back to when they were originally used in boar hunting and bull/bear baiting. When bull/bear baiting was outlawed, pitting them against each other became popular for entertainment, betting, etc., like cock fighting (also referred to as a sport).
In all the above activities, they are constantly handled by strangers, unlike, for instance, dogs bred for an activity like estate guarding or sheep guarding, which dogs are usually only handled by their regular handlers, and thus have no particular requirement to be docile towards strangers.
