My guess is he was someone who was introduced to Christianity, saw what he perceived to be flaws in the doctrine and tried to create a new Gnostic Christian sect based on select texts from the New Testament and his interpretations of it. This practice was common at the time and wasn't cracked down on until the 5th century CE. I should point out that this is how Christianity started as well. A group of people, probably Romans, decided to create a new, updated version of Judaism that was more compliant with their personal, and likely political, views. At the moment we can't push the date of any of the books in the New Testament any farther back than the 50's CE. At the time the Jews were threatening to revolt and finally did in 63CE leading the Romans to invade and ultimately burn down the temple of Jerusalem in 70CE. Is it really so far fetched to think that a group of Roman officials tried to pacify the Jews by attempting to convert them to a religion that puts blame on the Jewish community for the death of its savior and shows Rome in a somewhat positive light? All speculation on my part, I admit.
