Yeah, that’s the thing: “which language is spoken by the most people” is an easy question to answer, but “which language (or combination of languages) lets me communicate well enough to get by in the most places” is much harder because the statistics aren’t necessarily collected in a way that lend themselves to that kind of analysis.

For example, Hindi is spoken by a whole bunch of people, but I’m pretty sure the vast majority of those people also speak English, so if you already know English you don’t actually need to learn it.