https://www.babbel.com/en/magazine/language-most-words Basically, AFAIU if you count "real" words and not compound words that some languages allow by mashing together other words, or inflections (such as words modified by cases in Russian) English is pretty much accepted to have the largest vocabulary. If you do count compound words, then it's Finnish, which then technically has an infinite vocabulary by appending numbers to words to create a new compound word.
Apparently the Norman conquest is the main contributor. Anywayz it's a bit spooky / accident in history how English got to become so widespread. I mean it wasn't so long ago (around 1750) that Britain had a king (George 2) who didn't even speak English. He did spoke the respectable / civilized languages of the time: French, Latin and of course his native German. But English was so marginal and puny that even though he got "elected" king, he didn't consider worthy to learn it
George II learned English according to https://www.etymax.com/blog/the-que...res-a-lot-more-to-monarchs-than-meets-the-ear
I hope you are not mocking the monarchy... stay alert for cries of "Off with his head!". Or is that from the French Revolution, I was never quite sure.