If anyone’s interested, languages follow similar differentiation patterns as species in evolution. Ways this occurs include: allopatric (barrier separates past equivalents), peripatric (migration), and sympatric (subcultures), etc.

It’s the same reason Matthew Rhys can do a spot-on American accent despite having an outrageous Welsh accent irl: people are more likely to grow up on the media of more mainstream languge so it becomes the lingua franca. (love Rhys to clarify)