Why did the use of vernacular in literature spread during the renaissance?

In European literature, the growth of vernacular literature predates the Renaissance. English vernacular literature dates back to at least the 9th century and possibly earlier. In French, there was an enormous growth in vernacular literature from the 11th century onwards; in German, from the 12th century onwards. Dante, in De Vulgari Eloquentia (c. 1302), argued for the suitability of the vernacular in Italian, and demonstrated it with the Commedia. There is evidence of some literary vernacular in Spanish as early as the 9th century.

What is in many ways perhaps more interesting than the continued growth of vernacular literature in the Renaissance is the continued use of Latin, both as the language of learned discourse and as a literary vehicle, given new impetus by a revival of classical Latin.