Divorces were obviously not as easy to get in the Tudor era as they are today and there had to be a very good reason for annulling a marriage. It had taken Henry VIII around 7 years to annul his marriage to Catherine and that was with a pretty good argument, arguing that the Papal Dispensation that he had been given to marry his brother's widow was actually contrary to Biblical law. Even with that argument the Pope had still refused to grant Henry the divorce and Henry had been forced to break with Rome and get his own court to rule on the annulment. There was no way that Henry was going through that again. If he or Cromwell, or both of them, wanted to get rid of Anne then there needed to be a very good reason and she had to go for good. That is why, in my opinion, that Anne was accused of adultery, incest and plotting the King's death, she had to have committed treason and she had to be executed.