I can think of several big things:
1) The success of the British Empire, largely thanks to the quality of its navy, and in some cases its armies, and their successes in their struggles in particular with the Spanish.
which led to:
2) The success of the British colonies in North America, and their subsequent revolution and independence, and acquisition of the Louisiana Purchase, and their genocide of the native American populations and dominance of the most usable parts of the entire continent, all under the English language.
which led to:
3) America’s size and resources and separation by oceans from Europe and Japan, allowing it to decisively support the Allies (including Britain) in the two world wars of the 20th Century.
and
4) The spread of English-language media (movies, music, written publications, advertising, television, other products with labels written in English) on a massive scale, which is consumed by most or all smaller countries.