Herod is using Satan's playbook. He will not give up. Not content with having Herodias as his wife, he will lock up John in prison, and ultimately have John beheaded in a foolish satan-inspired promise to Herodias' daughter (cf, Matthew 14:1-12). Not only is Herod using Satan's playbook, he's serving as Satan's shill. Satan is using Herod, and he will be the worse for it.
Josephus says that Herod, "feared lest the great influence John had over the people might put it in his power and inclination to raise a rebellion; for they seemed ready to do anything he should advise." Whatever the reason - coopted by Satan, serving as his pawn, captured by fear - Herod will not give up. Even more so Satan. We must stand up to him. May God give us his Spirit of courage, strength, wisdom, and discernment.
