Why were the Bibles in Latin?

Bibles were in Latin because that was the official language of the Catholic Church. It also meant that only the educated people, (mainly priests or those working for the church), could interpret what was written in the book to the people. It was not only the Bible which was in Latin, most official documents, (deeds, land grants, etc.), were also in Latin, which required someone, often trained by the church, to read and write them.