“Then Satan entered into Judas called Iscariot, who was of the number of the twelve. He went away and conferred with the chief priests and officers how he might betray him to them. And they were glad, and agreed to give him money. So he consented and sought an opportunity to betray him to them in the absence of a crowd.” (Luke 22:3-6)
“Satan entered into Judas called Iscariot.” In other words Judas falls prey to the temptation. We don’t know why. But he does. Some think perhaps he was disillusioned. He was a zealot, which was a group of people who wanted war with Rome, and perhaps he saw that it wasn’t happening and wouldn’t with Jesus. There is perhaps the idea that he thought handing Jesus over would spur on the revolution, that the people would rise up and start taking things into their own hand. But whatever it was, the chief priests and officers were glad for the help, Jesus had too many supporters among the people to just go arrest him.