For decades, flatbreads have been consumed in the Mediterranean. The word “pizza” is clearly linked to the word “pita,” and it was popular in the Mediterranean. It was used interchangeably with focaccia and schiacciata by Italians.That isn’t to say it wasn’t discussed in southern Italy and Sicily much earlier. Water buffalo were introduced to Sicily at some stage, most likely by the Arabs in the 8th or 9th centuries. They were brought in for labour, and their milk was only used as a replacement for cow or goat milk by the poorest peasants.
Scappi mentioned a pizza napoletana, a sweet tart or pie with raisins, in the 1500s.
The Spanish introduced tomatoes from the New World to Europe in the 1500s. They eventually made their way to Italy. The name pomo d’oro comes from the fact that the early tomatoes were small and yellow. The earliest literary references in Italy date from the mid-fifteenth century in Tuscany.
People didn’t have ovens at home, so bakers made the majority of breads. Flatbreads were commonly sold, either plain or with a few toppings such as anchovies or onions, and tomatoes became a popular topping choice in the 1700s and 1800s. Usually, they were sold on the streets by dirty, filthy boys carrying boxes of pies. These were essentially the same pies mentioned by Virgil in the Aeneid, but produced in a different way.
The growing population was mostly destitute and men took any jobs they could find, as messengers, porters, or whatever. These men were called lazzaroni, because they were dressed in whatever rags they could get and were thought to resemble Lazarus in his tomb. Pizza was the perfect food for the lazzaroni.
Tomatoes were thought to be toxic until the 1600s, at the earliest. Peasants in the south of Italy and Sicily soon began to consume tomatoes. They were easy to grow and propagate, and by the 1700s, they were very popular.
“The pizza is a kind of talmouse like the ones they make in Saint-Denis. It is round, and kneaded from the same dough as bread . . . There are pizzas with oil, pizzas with different kinds of lard, pizzas with cheese, pizzas with tomatoes, and pizzas with little fish.”
Pizza was not well-liked in either the United States or Italy. It is not mentioned in Italian cookbooks from the early 1900s. In 1918, the term “pizzeria” first appeared in an Italian dictionary.
In the late 1800s, a lot of people left Naples and Sicily to come to America. Some of them brought the idea of pizza with them. Since there was no English word for the pie, the Americans just adopted the word “pizza”.
Nonetheless, because pizza is so closely identified with Naples, in 1984, a group of pizza makers in Naples decided to create a standards board and define what was real Neapolitan pizza. Basing their standards on a loose agreement of what they were already doing, they’ve claimed to be the birthplace of pizza and thus qualified to set the standard to be met.
So you have various possible answers to the question.