Why was Benjamin Franklin chosen as ambassador to France?

Because he was a good influence to other people

In France, the accomplished Franklin was feted throughout scientific and literary circles and he quickly became a fixture in high society. While his personal achievements were celebrated, Franklin’s diplomatic success in France was slow in coming. Although it had been secretly aiding the Patriot cause since the outbreak of the American Revolution, France felt it could not openly declare a formal allegiance with the United States until they were assured of an American victory over the British.