Pope Clement VII refused to grant Henry an annulment of his marriage.
Henry wanted a male heir.
Henry wanted a different wife.
Catholic AnswerIt started out for purely political reasons, as mentioned above. The Pope ruled that the King was validly married to Catherine of Aagorn and could not get an annulment (a decree that no valid marriage ever existed) and Henry wanted to marry again to get a male heir, he already had a daughter. So Henry made parliament the "head" of the "church" in England so that they could grant him an annulment.