One theory is that Judas was a Zealot, a strong Jewish patriot who wanted to prod Jesus into action against Rome. For Jews, the Messiah did not come to die for our sins but to re-establish the Davidic throne, and to do so the Messiah needed to take dramatic political action. Judas' possible identification as a Zealot is indicated by two bits of evidence: his name "Iscariot" may be related to the word for the faction of Zealots know as the 'sicarii,' meaning dagger-men. Also, in the Epistula ApostolorumEpistula Apostolorum vs.verse 2, [2nd century] Judas is called Judas Zelotes, andan appellation usually associated with another apostle, Simon the Zealot. In this view, Judas believed Jesus was indeed the Jewish Messiah who had divine power, and by turning Jesus over to the Romans, Judas thought he would move Jesus to dramatic action.
The Gospel of John suggests another possible motivation for Judas: financial corruption. John 12:3-6 states:
Mary [of Bethany] took a pound of costly perfume made of pure nard, anointed Jesus’s feet, and wiped them with her hair... [But Judas] said, 5 “Why was this perfume not sold for three hundred denarii and the money given to the poor?” 6 (He said this not because he cared about the poor but because he was a thief; he kept the common purse and used to steal what was put into it.)
3 Mary [of Bethany] took a pound of costly perfume made of pure nard, anointed Jesus’s feet, and wiped them with her hair... [But Judas] said, 5 “Why was this perfume not sold for three hundred denarii and the money given to the poor?” 6 (He said this not because he cared about the poor but because he was a thief; he kept the common purse and used to steal what was put into it.)
-Jesus said to Judas "You'll do more than all of them, because you'll sacrifice the human who bears me. Your horn has already been raised, your anger has been kindled, your star has ascended..." vs. 56
Jesus said to Judas "You'll do more than all of them, because you'll sacrifice the human who bears me. Your horn has already been raised, your anger has been kindled, your star has ascended..." verse 56
My answer in summaryMy answer in summary: there are several ways that Christians might explain why Judas betrayed Jesus despite witnessing God's power in him. They include that he was God's agent in doing so, that he was a Zealot who wanted Jesus to use God's miraculous power against Rome, that he was greedy and wanted money, that he lost faith because he thought Jesus himself was misusing money, that he was outraged or jealous over Mary of Bethany's intimacy with Jesus, or even that he and Jesus were both divine messengers and not normal human beings. These explanations are not mutually exclusive.