Several decades ago, there were efforts to make French the international language, since it was already spoken on every continent.  That is why, to this day, Air Mail is usually marked "Par Avion".

However, since then, the United States turned into the most influential nation on the world's economies.  The people in most industrial countries learned English to more easily conduct business with the U.S.  I have called shopkeepers in other countries and found that they are usually fluent speakers of English.  It has become the international language.