“The role of the Messiah was to unite the twelve tribes and establish a kingdom of Israel. If he didn’t do that (which he didn’t) then he didn’t fulfill their prophecy”
That was what the Pharisees and Sadducees of the times always had interpreted the prophecies to read...but Jesus said to Pilate..”My kingdom is not of this world, if it was my servants would fight...”
Christ was of the Priestly order of Melchizidek, but the religious leaders of his times were expecting a King and Judge acting out of the priestly order of Aaron and the Levitical lines.
Whether you believe or not is one thing, but we have Jesus own words, at least as depicted in the Bible we have...(whether you believe it or not) who defined his own role to Nicodemus in John 3:16 “For God so loved the World, he gave his only begotten(conceived by the Holy Spirit) Son, that whosoever believes in Him would perish but have everlasting life.
I know you are skeptical of Christianity’s claims, but it least for the narrative’s sake, don’t take Jesus’ own words out of context. Though he came to preach to the Jews first, his ultimate mission was to seek and save that which was lost through out the world. World conquest via a vengeful Messiah was never to be Jesus’ mission. The saving of the world’s lost was Christ’s mission. Even though you are a religious skeptic, at least understand through Christ’s own words(you might qualify them as purported, being a skeptic and “stuff”) what his mission was and still is!
At best we can say of Jesus: there are several records to suggest that he lived, he traveled about, he spoke to Jews, he was thought to be capable of ruling Israel, he was killed by political enemies, the end.
Most New Testament accounts are a garbled mish-mash that suggests a combination of attempts to make him the fulfillment of OT prophecy (probably included at the time) and later attempts to suggest his mission was something else entirely (probably concocted later.) That no one thought to expunge specific King of Israel referents at the time is explicable by remembering that those who compiled the Bible were not Jewish and probably didn't recognize the significance of certain elements (such as Joseph not being Jesus real father --see: Curse of Solomon.)
I would add that if he was on trial for his life, I hope that's what he'd say. Only a moron would say "Yes, I'm here to mount a revolution and overthrow your rule. Is there a problem?"