After the Second World War, the story increasingly becomes one of demographics and geopolitics.

In contrast to the comparatively plurilingual approach of the sprawling British empire during the 19th century, scientists from the rising American empire of the 20th were not expected to acquire competence in foreign languages. The massive bulk of Soviet scientists and engineers that rose up after the war, however, presented the US with a new scientific competitor. In the 1950s and ’60s, with about 25 per cent of world publication, Russian became the second most dominant scientific language, trailing the 60 per cent of English. But by the 1970s the percentage of Russian publications began to drop as scientists worldwide blazed the trail to Anglophonia.

The American inability – or refusal – to learn Russian, let alone other foreign languages, in order to conduct their science, combined with the export of an Americanised science system across the Atlantic to Anglophone and non-Anglophone countries alike, further propelled the Anglicisation of science. The willingness of Europeans, Latin Americans and others to accede to this new monolingual regime also played a role. Since they wanted to be cited by the leaders of the field, the Dutch, Scandinavians and Iberians ceased publishing in French or German and switched to English. Paradoxically, publishing in anything other than English came to be seen as a manifestation of nationalist particularism: no one published in French who was not natively Francophone; mutatis mutandis for German.

GOOD QUESTION

Demographics and geopolitics.

well. or the other thing white people forget to mention: Colonialism.  

but maybe that was discounted in the passage above.

It was. Mentioned several times in the article too.