Why did king Henry divorce execute his wives?

Anne Boleyn and Katherine Howard were executed for committing crimes agains the king. Anne was beheaded for High treason (betraying the trust of the king), Adultery and Incest - none of which were infact true. Katherine was executed for High treason and Adultery - no one is completley sure about the validity of the accusation of treason but the adultery was certainly true. It is famously known that whilst married to the king, Katherine became the mistress of Thomas Culpepper. She had also been betrothed to Francis Dereham and had not admitted this to the king, therefore their marriage had been null and void in the eyes of God from the start. This actually means that King Henry had no right to execute her on the grounds of adultery as they were never formally married and it was not a religiously bound marriage contract.

hope this helps :)