French was the official diplomatic language of the Western world for quite a while (the "lingua franca", a phrase that now means "official language" or "common language"). That was due to the success of Charlemagne, French catholicism, and William the Conqueror. British English supplanted French over a period of time that began with the defeat of the Spanish Armada during the 1500's. The defeat of Napolean and the British colonization of India (plus their domination of the Chinese opium market and much of the Southeast Asian spice market) in the period from 1700-1850 continued the linguistic takeover. Add to that the previously mentionned spread of English colonists to the New World, Australia, New Zealand, then their colonization of North Africa and parts of the Middle East... That quote about the sun never setting on the British Empire has meaning. Britain had colonies or economic control of many regions of the world, and its language went with it. With the rise of the US as a world power from 1918 onward, the dominance of English as a diplomatic language was assured. It is interesting to note, however, that more people speak Chinese as their native language, and I think that's still true of Spanish, due to the Latin American population.
Regarding the odds spellings: English did not have fixed spellings until the 1800's, when standardized dictionaries began to appear. The people who created the dictionaries cribbed from each other but did not form committees. It simply happened that the most popular dictionaries won! The French L'Academie Franciase attempts to keep modern French pure, though the general populace happily ignores the official attempts to purge such words as le pique-nique, le week-end, and l'hambergeur. North Korean, I have read, is a manufacturered language, at least as far as the spelling goes. Apparently the previous Kim created a completely new set of characters and, as supreme dictator, forced it on the nation. All words were respelled phonetically using the new characters. This makes it the easiest language to learn to write (if you start as a child, at least).
By the way, when Norman French took over from Anglo-Saxon, it turned many everyday Saxon terms into vulgar (that is, dirty) words. Sh*t, for example, was merely the Saxon word for feces, no stronger in meaning that the French merde is today. The same applies to many other four-letter words of Saxon descent.
As a final irony, the Normans were originally cousins to the Anglo-Saxons. They were raiders from the North (Jutland, Saxony, etc.) who colonized the northern coast of what we now call France at about the same time that the first Jutes and Saxons were invading England. But the very name, France, is also a conqueror's term. The Franks, a Germanic tribe, moved south overland and took over the geographic region of France from the Gauls in early AD (hastening the fall of Rome), long before their distant cousins the Normans descended on them in turn. With each invasion and assimilation, the languages changed. That's one of the things that makes them so fascinating, eh?
