This is a way to refer to people from every social status. Here "least" and "greatest" represent those who are least important and those who are most important. AT: "all the people from every social status" or "all the people, including the least important and the most important people" (See: [[rc://en/ta/man/translate/figs-merism]])
Most likely not every individual in the town went. The word "all" is a generalization that means very many people went. AT: "many other people" (See: [[rc://en/ta/man/translate/figs-hyperbole]])