There were many lingua francas of which French was supposedly the first global lingua franca. That changed and it became English (from what I understand). We will probably see another language become the lingua franca, so my question is: should it be English? Are there better candidates out there? Why / why not?
It’s because of the network effect. If you only know your local language and want to unlock speaking to the rest of the world when learning English gets you pretty far.
A lot of people start learning English because a lot of people speak English. Since now Europe, North America, half of Africa, Middle East, South Asia, Latin America, Oceania speak English to some extent that I know of.
It’s absolutely bonkers how far English has gotten in one generation so learning anything else as a second language is pretty weird.