I suppose there were a few options. One stuck and that was English. Realistically it could have also been Dutch before it would be Italian.
There are no "options." Nations don't always choose an "official" language. They just conduct their affairs in the language of the group in power, or, with rare exceptions, the majority population.
Of course the exceptions are astounding.
- The Aramaeans vanished and were absorbed into the Assyrian-Babylonian people, but their language continued to be the lingua franca of the Middle East for nearly 3,000 years, through the rise and fall of many empires, right up into the early 20th century.
- The Normans invaded England in 1066CE, overthrew the government and made French the national language. Yet within 300 years they had intermarried with the native population and begun speaking English. This would be equivalent to the Spaniards adopting the languages of the Aztec and Inca so that they would now be the official languages of Mexico and Peru.
Some nations do adopt official languages, but it's usually for the purpose of elevating two or more to that status, in order to maintain harmony among diverse ethnic groups. French, German and Italian are all official languages in Switzerland, French and Flemish (the politically correct but linguistically incorrect name for the Belgian dialect of Dutch) have that status in Belgium, and in the former nation of Czechoslovakia both Czech and Slovak were official.
I think that English is easier though . . . .
English is not easy for everyone. It has one of the largest sets of phonemes (individual sounds) of all languages, making it difficult for many people to distinguish between two similar words (e.g. bit/beat, there/dare, Aleutian/allusion), and the way we cram phonemes together almost arbitrarily makes many words difficult for them to pronounce (e.g. squirrel, tasks). Our prepositions often carry almost no meaning at all, yet the rigid rules for their use seem designed for no purpose other than the easy identification of foreign speakers. (I always ask English speakers to explain the difference between "on time" and "in time" and so far only one has managed to do it.)
English is relatively easy for speakers of Chinese, which shares our subject-verb-object syntax and has no inflections for masculine/feminine, present/past/future, singular/plural, etc. But it's very difficult for speakers of Japanese, which has a topic-description syntax and inflects verbs for the difference in social class between the speaker and the person spoken to--and in which two consonants can never be adjacent (except N). It's easy for speakers of French, which shares half of our vocabulary and most of our phonemes, but hard for speakers of Russian, which has only seven vowels and is not dominated by French, Latin and Greek words. It's very difficult for the Hopi, who have a lot of trouble grasping our concept of time.
. . . . and in song may sound better, for some reason.
That's just personal and/or cultural preference. Every language's songs have their charms.
