I do think it is funny that the French blocked a minor language from becoming the language of diplomacy just to watch helplessly as it is replaced by English.
Isn't Klingonese more popular than Esperanto now?
The problem was/is practically no one speaks it.
According to Ethnologue (for many proffesionals the refference for language statistics) there are at least 2 million fluent speakers of Esperanto today around the world, and there are at least 1,000 confirmed people who speak the language natively (including apparently George Soros), most of these are consentrated in "Japan, China, France, Germany, Italy, Poland, United States, Brazil, Belgium, and United Kingdom" (https://www.ethnologue.com/language/epo). I personally think this is a little optimistic and other sources usually state that there are between 1-2 million fluent speakers. By comparison apparently fluent Klingon speakers are in the hundreds or possibly over one thousand at best. Honestly the fact that a constructed language is this popular to begin with is completely mindboggling to me. Let alone that it was almost wiped out in WW2 (Nazi Germany actually sent at least a few thousand Esperanto speakers to camps, including two of Zamenhof's daughters, mostly because their internationalist cause was considered threatening and because of its association with socialism). I won't lie I feel like most of the people on this thread are pretty ignorant of just how large the Esperanto speaking community was prior to WW2, it could have seriously become a widespread langugage at least in Europe if not around the world. Peesuming the League adopts it it could end up widespread enough to survive WW2 relatively well, whether or not it would have been as popular as say, English is another matter, although for instance I can imagine the post-Stalin communist bloc encouriging the use of the language if it's widespread enough. Some former african colonies adopting it as a way to distance themselves from their former colonial nations as well as to fasciliate communication throughout the continent as a lingua franca of sorts (although likely no the only lingua franca used) is also possible.