

It was (the first world wide language used for diplomacy). If you want to quote Wikipedia, then:
“French is sometimes regarded as the first global lingua franca, having supplanted Latin as the prestige language of politics, trade, education, diplomacy, and military in early modern Europe and later spreading around the world with the establishment of the French colonial empire. With France emerging as the leading political, economic, and cultural power of Europe in the 16th century, the language was adopted by royal courts throughout the continent, including the United Kingdom, Sweden, and Russia, and as the language of communication between European academics, merchants, and diplomats.”
https://en.wikipedia.org/wiki/Lingua_franca#French
Maybe sailors communicated with locals through a broken pidgin, but diplomats and aristocrats used French.
Yes, learning a few letters that form syllables and through that you can read words even though you don’t know what they mean is not practical, it’s better to learn a some thousand symbols and, if you don’t know a symbol at all, you can’t even say it out loud because you can’t read it.
Ideograms are the imperial units of language.