The vulgar of different European places was already splintered into very different variants many centuries before the 1400s, it just matured from a continuum of

The vulgar of different European places was already splintered into very different variants many centuries before the 1400s, it just matured from a continuum of random informal dialects, the further you travel the better linguist you have to be, to more consolidated and more recognized languages (plenty of different ones in "France" and "Spain").