[18.116] Now some of the Jews thought that the destruction of Herod's army came from God as a just punishment of what Herod had done against John, who was called the Baptist.
[18.117] For Herod had killed this good man, who had commanded the Jews to exercise virtue, righteousness towards one another and piety towards God. For only thus, in John's opinion, would the baptism he administered be acceptable to God, namely, if they used it to obtain not pardon for some sins but rather the cleansing of their bodies, inasmuch as it was taken for granted that their souls had already been purified by justice.
[18.118] Now many people came in crowds to him, for they were greatly moved by his words. Herod, who feared that the great influence John had over the masses might put them into his power and enable him to raise a rebellion (for they seemed ready to do anything he should advise), thought it best to put him to death. In this way, he might prevent any mischief John might cause, and not bring himself into difficulties by sparing a man who might make him repent of it when it would be too late.
[18.119] Accordingly John was sent as a prisoner, out of Herod's suspicious temper, to Machaerus, the castle I already mentioned, and was put to death. Now the Jews thought that the destruction of his army was sent as a punishment upon Herod, and a mark of God's displeasure with him.
Note the motivation is not his wife's anger nor his own evil designs but concern for rebellion because of the cultlike control John had over his followers. Also, John is removed from Antipas' presence and relocated to the castle in Galilee where he is seemingly immediately executed in an unknow fashion. No birthday, no dance.
You, upon reading, must have noticed the doublet (JTB being reason for Antipas' loss) and the strange adoration of the JTB who is otherwise being described as a potential threat to the Roman order. Recall who Josephus was. He was a Jewish general that switched sides and commissioned to describe the history of his people for Vespasian. He spent his career promoting the Roman system and allegiance. Maybe you can see why some suspect the passage has been altered. Further, as described in the link above, the pious language of the meaning of baptism is more than peculiar in this setting.
So what we have is a description of the death of JTB that differs from those found in the Gospels. The link above also offers a suggestion that the Christian who interpolated the JTB reference was from an early Ebionite or some other Jewish Christian sect and not from one that used a form of the Synoptics we are familiar with. Maybe, other gospels from that time do not mention it.
It is worth mentioning the intertextual nature of the execution scene. It's been recognized for centuries to have been inspired by the Esther story and the Elijah/Jezebel animosity of the OT.
