Clearly, Jesus believed he was some sort of precursor to the Jewish Messiah. (Not the spiritual idea of the Messiah that Christians later invented, but The Messiah that Jews of Jesus's day and today think about — a human, non-divine, political leader who would overthrow foreign oppression of Jerusalem and surrounding Jewish territories, and who would establish world peace.)

When Jesus called himself the Son of Man, he was echoing Jewish thought about a mythical figure who would usher in that human Messiah.

The Romans executed him for that as a political dissident.