Whether two ways of speaking count as 'one language' often isn't about linguistics

Danish, Swedish and Norwegian speakers can largely understand each other, yet are classified as three separate languages because they're spoken in three separate countries. Meanwhile, Mandarin and Cantonese speakers often can't understand each other's speech at all, yet are classified as dialects of one Chinese language. Political borders decide the label at least as much as mutual intelligibility does.

— Linguistic and sociolinguistic record, Mutual intelligibility — Dialect vs. language classification