I suppose you are asking about the internal forces that motivated and finally moved Judas to hand over Jesus to the Jewish leaders. We could say a few things, but it is difficult to provide a final answer to your question.
1. A Long Process:
We have to assume that Judas joined the disciples because he was moved by Christ’s loving character and the power He displayed during His ministry (Matt. 10:4). Like the other disciples, Judas came to Him with imperfections, but he never overcame them. The most pernicious one was avarice, which blinded him to the true nature of the work of Christ (John 12:6; cf. Matt. 26:15). After about a year with Jesus, Judas may have been expressing his frustrations to the disciples and perhaps criticizing Jesus’ work behind the scenes (cf. Mark 10:13, 14). This led Jesus to ask a rhetorical question to the disciples: “Did I Myself not choose you, the twelve? And yet one of you is a devil [diabolos, “slanderer, adversary”]” (John 6:70, NASB).* At this point Judas was not yet thinking about betraying Him (verse 71; cf. Luke 6:16).
Judas’ frustration with the direction of the work of Jesus reached an important point after Mary anointed Him with an expensive perfume. He hid his true contention, but his selfishness was revealed, and Jesus kindly reprimanded Him (John 12:5-8). This time Judas went to the Jewish leaders “to betray Him to them” (Mark 14:10; Matt. 26:14). By the time of the Last Supper, the devil had “already put it into the heart of Judas . . . to betray Him” (John 13:2). The point of no return arrived when during the supper Jesus identified him as the traitor. “Satan [then] entered into” Judas (verse 27, NIV), and he “went out immediately. And it was night” (verse 30).
2. The Motivation:
It seems safe to say that Judas was controlled by selfishness and avarice, and that this led him to betray Jesus. First, we can assume that Judas, like the rest of the disciples, believed that Jesus was a political messiah who would deliver the people from the Romans. Joining Him could assure Judas an important role in the kingdom of Jesus. Second, Judas soon began to realize that Jesus’ views of His kingdom were of a spiritual, not military, nature, and this frustrated him (John 6:26-71). It appears that after the failed attempt of the people to make Jesus king by force, Judas began to question whether he should continue to be loyal to Jesus (verses 14, 15, 70, 71). Third, Judas probably disliked that Jesus was announcing His death, an idea incompatible with Judas’ military messiah (cf. Mark 14:8, 10). Fourth, we know that in handing Jesus over, Judas was hoping that, as in other occasions, Jesus would escape (Matt. 27:3) and thus perhaps precipitate a manifestation of Jesus as a military messiah. During His arrest it was clear that Jesus could have escaped, but He did not (John 18:5-8). His display of power demonstrated that He, not the soldiers or Judas, was in control of His future. When Judas realized that Jesus was going to be killed, he tried to stop what he thought he had initiated (Matt. 27:3, 4), but it was too late; Jesus had come to die. Out of deep guilt, Judas went out and took his own life (verse 5). Yes, Judas wanted a place in Christ’s military kingdom for personal gain, but not in a spiritual kingdom. Judas never understood that Jesus’ mission was to give His life for those who will be part of His eternal kingdom.