They hated him because Denmark basically had a regal cult and Struense was more or less openly cuckolding the king. While the reason for the aristocratic resistance to his rule was his liberal reform spree, he was convicted of lese majeste and that was what the press was mostly mad about. One of the big accusations was that he had beaten the king, which was somewhere between unthinkable and heretical.

Somewhat ironically the king’s son would later take power by actually beating the person behind the arrest of struense who had installed himself as regent.