Why did King Henry exucuted 2 of his wifes?

King Henry VIII of England executed two of his wives, Anne Boleyn and Catherine Howard. Anne Boleyn, his second wife, was executed on charges of incest, adultery, and treason though the evidence for those crimes is not very good and it is theorized it is because she did not have a male heir for Henry. Catherine Howard, his fifth wife, did commit adultery and was executed on charges of adultery and treason.