What happened to Judas Iscariot? Was he originally a believer then Satan put it in his heart to betray Jesus? Do you think that if Judas never existed that God would have allowed or made one of Jesus’ other disciples betray Him?
First, was Judas a believer? There are many verses that taken together are convincing that Judas was not a believer in the true sense. Matthew 7:21-23 is a good place to start. Three things need to be noticed. First, “Lord, Lord” is an open profession. But, does that mean there is real faith? Second, the profession even brings good works as evidence. Finally, the Lord says “I never knew you. (My emphasis.) So, in spite of profession and even good works, we have to conclude that there was never a vital relationship as described in John 1:12,13. Other verses to consider are: Luke 22:3; John 6:70, 13:2,10,11; 17:12; and Acts 1:25. Judas no doubt believed in a superficial way. Many did so. (See for example John 2:23-25 and John 6:66-71.) Yet, they were not real. So, in this way Judas is a very solemn lesson for us. We need to preach a clear gospel and seek to help people understand it. But, it is God’s work in the heart that is necessary for true repentance and salvation.
The second part of your question brings up two serious issues regarding the condition of Judas and the Lord’s dealing with him.
First, the Lord chose Judas as a disciple knowing what he was and what he would do. As Son of God, He is both sovereign and had perfect foreknowledge. (John 6:70,71) In addition, the Scriptures must be fulfilled which prophesied of the betrayal. (Ps 41:9). God is not willing that any should perish, yet He cannot set aside the nature of the creatures He has created by overruling their will. (I recommend Determined to Believe?, by John C Lennox for a discussion of the issue of God’s sovereignty and man’s responsibility.)
Second, “what if Judas never existed?” In fact, Judas is not all that special. Think of the railing on the Internet (e.g., YouTube) against Christ. Some even go so far as to claim that there is no evidence that Jesus of Nazareth ever existed! This, against all reasonable evaluation of historical documents. Judas essentially took the same position in being self-blinded to Jesus’ plain statements about Himself. So, Judas is a solemn picture of “everyman.” He was the modern equivalent of Cain. He demonstrates that even being face to face for three years with the manifestation of “the Father” as seen in Christ was not sufficient to convince him. He thus is like those today who claim “If God would just reveal Himself, I would believe.” Judas is proof of the folly of such a claim. If one will not believe on the basis of the written word of God they will not believe if God Himself stood before them. See Luke 16:31.