Matthew 26.14-16: Then one of the twelve, Judas Iscariot, went to the chief priests, (15) and said, “What are you willing to give me if I deliver Him to you?” And they counted out to him thirty pieces of silver. (16) So from that time he sought opportunity to betray Him. (NKJV)
Just prior to the above verses, the chief priests, scribes, and elders of the people had made a decision at the palace of the High Priest to arrest Jesus and kill Him. They appear not to have taken any action regarding this plot before Judas Iscariot came to them by his own initiative. And he invited them to make the first proposal of the fee they would give him for delivering Jesus to them.
I believe this act of betrayal was born out of greed. Strictly for money. I see no point of trying to make excuses for him along the line of his being disillusioned in the way Jesus carried out His mission. The Gospel of John 12.6 says that Judas was a thief. Judas Iscariot was a deceiver, betrayer, and a seeker of money.
The payment of 30 pieces of silver by these leaders was the fulfillment of the prophecy of Zechariah 11.12. The chief priests, by their own action of choosing 30 pieces of silver contributed to another fulfillment of prophecy regarding Jesus as the true Messiah of God.