1. They didn’t know English or Yiddish.
2. Unless you are an American, it’s easy to learn languages.
3. They probably only knew those of people in the immediate region. I doubt they had any reason to chat with an American Indian or an Australian Aboriginee.
4. The Rosetta stone only had Egyptian and Greek, and wasn’t intended as a teaching device (it as a bilingual text in a region that was bilingual).