Let’s pull some pieces together from the Gospels:
The disciples were forbidden to carry money – but Judas kept the movement’s money. He had a special relationship with Jesus, and a special place in the movement.
Zealots, being egalitarian and recognizing only God as their Lord, called each other “Friend”. Judas is the only disciple addressed as “Friend” by Jesus.
Judas led the Romans to Jesus, but not necessarily of his own free will. He died violently immediately afterward. He was found hanged (Matthew) and with his belly split open and his guts spilled out (Acts). The Romans claimed it was suicide.
Judas is called “Iscariot” in the New Testament. That name is obscure in meaning, and there have been suggestions that he must have come from the town of Karioth. Unfortunately, there is no record of exactly such a town name. In ‘The Gospel According to the Romans’ I suggest that the name is a deliberate corruption of “Sicariot”, to disguise the name of this very important person in Jesus’ story. A sica is a curved knife, the weapon of choice of urban guerrillas. A “sicariot” is a “dagger man”.
“Sicariot” was the common derogatory term for a Zealot, the armed resistance against the Roman occupation of Israel. Other terms used by the Romans were “thief” and “robber”.
When Paul tried to spread his new religion into the Roman population at large, links between Jesus and the Zealots were problematic. Distortion and misdirection were necessary in a retelling of the story from which the Romans were largely omitted. Judas was too well-known to ignore; but at least his name and his role could be shifted, from Jesus’ friend the “Sicariot”, to Jesus’ betrayer the “Iscariot”.