Why does the author think the gospels say that the governor executed Baptist because he criticized his sexual activities?

The author suggests that the Baptist's teachings were a more likely trigger for his execution than the reason given in the Bible such as his moralistic condemnation of the governor's sexual activity. The latter, the author further suggests, was additional manipulation undertaken by the authors of the Gospels to achieve theological goals such as defining parallels between the Baptist's teachings and those of Jesus.