Antipas" passion for Herodias conflicted with his respect for and interest in John. He wanted to maintain both relationships, and tension arose as a result. [source][source][source]
"Kingliness changed places: the subject did not fear the sovereign; the sovereign feared the subject." [1][source]
Antipas could live with this tension, but Herodias could not, so she sought to kill her rival. Antipas evidently protected John from Herodias, the latter day Jezebel. John was righteous in his relations with other people and holy in his relationship to God. The perplexity the king felt undoubtedly arose over his conflicting affections for Herodias and John. Sometimes unrepentant sinners are curious about spiritual matters and spiritual people. This seems to have been true of Antipas. Probably the king and John conversed when Herod visited the Machaerus fortress east of the Jordan River where John was a prisoner. Its site in southern Perea, south of the north end of the Dead Sea, overlooked that Sea. This was probably the site of this whole event. [2][source]
"Herod was awed by the purity of John"s character, feared him as the bad fear the good." [3][source]