ETA: They lost WW1 too, but German remained our #1 foreign language.
Which in our case is false. We stopped learning German as a second language because of the Nazi aggression and atrocities during WW2, and started learning English as a second language due to their aid and closer relations during the war.
But yes, it's obviously not because of any linguistic merit.
No significant minority of ethnic Germans, and I think trade with Germany and the UK was roughly comparable.
In the 19th and early 20th century the British owned the seas, a post 1945 another English speaking country has - the United States.
Ironically the one biggest thing which presents an ideological advantage for Esperanto is that it's native to no nation, so all the people who speak it are closer to being equals in that regard; yet it is the imperialism and a large number of native speakers which has helped to make English so prevalent. So just being technically and morally superior doesn't win you adoption by a long shot, even if you try.
And it may be of note for this post that the original author of Esperanto was very conscious of this whole formal/informal issue, which is why he opted to introduce only the plural second person pronoun into practice.
Not saying that this is it's main problem, and other constructed languages like Lojban are probably even less relevant despite trying to be more "culturally neutral".
Even then, it's a very big jump from ‘people in some countries already know this and don’t need to learn at all’ to ‘people in some countries will have an easier time learning since they’ll recognise a lot of the words’; making this jump would already be a great improvement upon the status quo. Out of the languages which make the jump, Esperanto is by far the most widely spoken and otherwise used in practice.
But as an international language? I think having everyone learn something that is comparatively easy to learn is certainly more fair than having most people learn something that is comparatively hard to learn and understood by others from the get-go, thereby giving the latter an unfair advantage. And I feel that being more fair in this regard is indeed morally superior.
(Then again, that might just boil down to one's own idea of morality. But I feel like this one shouldn't be all too uncommon, and the claim is entirely reasonable in its terms.)
When my dad did his chemistry degrees (a bachelors and a masters by research) in the late 1960s / early 1970s (Australia), they made him do a unit on how to read German, because that is the language of a lot of the older chemistry literature. I don’t think they care anywhere near as much about German in chemistry nowadays, although (from what I understand) learning to read German is still an expectation for some humanities PhDs (such as Egyptology)
Seems a bit quaint now - but at least it got me to learn German and even spend six months studying at the University of Heidelberg.
We all speak English because at one point the English practically owned the entire planet.