In his actions and teachings, Jesus resembled John the Baptist. It would be logical to conclude that Jesus was a follower of John the Baptist. But that is not the conclusion of King Herod. We are speaking of Herod Antipas, not his father (Herod the Great).
Herod Antipater, known by the nickname Antipas, was a 1st-century ruler of Galilee and Perea. He bore the title of tetrarch and is referred to as both "Herod the Tetrarch" and "King Herod" in the New Testament though he never held the title of king.
Was Herod Antipater--called "King Herod" by Mark--insane? The gospel writers never question Herod's sanity. Yet Mark reports that Herod thinks Jesus is the resurrected John the Baptist. We might say this is a crazy conclusion--or we could say resurrections were so common at that time that Herod was thinking logically. After all, the Bible does have many resurrections passages.
But, of course, this part of the New Testament is fiction. After all, the anonymous writer of this gospel from around 70 CE was not at Herod’s court and had no way of knowing what Herod said 40 years earlier. Are we supposed to believe that Herod's comments were written down in 30 CE in official court documents and that "Mark" had access to court documents in 70 CE? Or are we to believe that "Mark" interviewed eye witnesses who remembered this four decades later?
The passage in question (Mark 6:14-16) indicates that the gospel writer was obsessed with resurrection. Herod Antipas was not.
Mark 6:14-16
King Herod heard about this, for Jesus’ name had become well known. Some were saying, “John the Baptist has been raised from the dead, and that is why miraculous powers are at work in him.” Others said, “He is Elijah.” Still others claimed, “He is a prophet, like one of the prophets of long ago.” But when Herod heard this, he said, “John, whom I beheaded, has been raised from the dead!”
The Bible describes a culture in which resurrections happened on a regular basis, so Herod jumping to the conclusion that Jesus is the resurrected John the Baptist is not surprising.
What is surprising is the Bible indicating that resurrections were common in that part of the world, yet not non-Biblical sources are silent about these resurrections. After all, Roman and Greek manuscripts also give us a view into the world at that time, but only Jewish writers indicate how common resurrection used to be.
Here are the Bible's resurrections in correct order:
1. Son of Zarephath widow raised by Elijah (1 Kings 17:17-24)
2. Son of a Shunammite woman raised by Elijah (2 Kings 4:32-35)
3. Man raised by Elisha’s bones (2 Kings 13:20-21)
4. Jairus’ daughter raised by Jesus (Mark 5:21-43, Matt. 9:18-26, Luke)
5. Son of the widow of Nain raised by Jesus (Luke 7:11-15)
6. Lazarus raised by Jesus (John 11:1-44)
7. “Many saints” rise around Easter (Matt. 27:50-53)
8. Jesus (four canonical gospels, Paul’s 7 genuine letters)
9. Dorcas raised by Peter (Acts 9:36-41)
10. Eutychus raised by Paul (Acts 20:9-10)
King Herod’s view of Jesus (Mark 6:14-16)--Jesus is John the Baptist resurrected! Herod Antipas