Did they sound poetic even to the 17th century ear?
They would do the translation and then it would be read out loud to see how it flowed.
This was a time when most people did not read (books were expensive!) so things were read to them. The end result was that thing that were meant to be read to others were written in a way that allowed the words to flow and (not incidentally) stick in your mind. Things that were meant to be read silently were written in a different manner.