The Bard and The Bible: Why doth Shakespeare so oft the bible quote?

Why was Shakespeare so fixated on the story of Cain and Abel in particular and on the theme of fratricide in general? 

Why do so many biblical verses about animals populate the Bard’s plays?

Why is the bible so often quoted by Shakespeare?

Exploring these and other themes will help us understand Shakespeare better, the Tanach better and give us insights that we can use in our own lives today.