Mark explains the moral and religious reason for the arrest and execution of John the Baptist. The Jewish historian Josephus gives a political reason instead. He says Herod feared that John’s popularity might lead to a rebellion (Josephus, Antiquities 18.5.2).
In a similar way, the charges against Jesus began as religious concerns (Mark 14:63–64). But when he was brought before Pontius Pilate, the charges became political (15:2; Luke 23:2–3).
It is not lawful: John said that Herod’s marriage was wrong. It was adultery (Leviticus 20:10). It also broke the law that forbids a man from marrying his brother’s wife (Leviticus 18:16; 20:21).