All the sources are long after the event and refer to his followers not to the man.
Like I said an impact crater.
If you follow the ripples you get to a point where there seems to be an event only the event isn't there (unlike John The Baptist or Paul where the paper trail leads right to the foot a flesh and blood man).
The same is true with King Arthur. Everything was written long after the event but what connects points to a possible Romano-Brit in Wales uniting local chiefs against Northern invaders or a distorted memory of Carausius. But everything else comes from other myths and legends from all over Europe.
Of Jesus and Buddha.
* Born as an incarnate god.
* Born from a virgin mother.
* Birth claimed as a divine event and prophesied as the same.
* Birth attended by singing angels.
* Birth attended by wise men bearing gifts.
* Prodigious childhood.
* As a child astounded teachers with knowledge.
* Fasted in the wilderness for forty days.
* Tempted while alone by the Tempter/Mara.
* Resisted the Tempter/Mara successfully.
* After the Tempter/Mara left, supernatural events occurred.
* Began ministry at thirty years of age.
* Attract large following mostly from lower classes.
* Attracted disciples who traveled with him.
* Attracted one disciple who was treacherous.
* Changed disciples' names.
* Encouraged celibacy for their disciples.
* Consecrated in a holy river.
* Itinerant ministry instead of at a fixed place.
* Performed miracles such as curing blindness.
* Renounced worldly riches and required the same of their disciples.
* Ministered to outcasts.
* Advocated universal love and peace.
* Taught mostly through use of parables.
* Triumphal entries (in Jerusalem and Rajagripa).
* Gave major sermon from a mound.
* Disregarded by the dominant religious elite (Pharisees and Brahmans).
* Just before death dispatched disciples to preach in other areas.
* Death accompanied by supernatural event.
Both Jesus and Buddha issued moral commandments that prohibited killing, stealing, adultery, false witness, and coveting. Both emphasized the same moral themes: advocate peace, not war; avoid the corruption of wealth; help the poor; abolish slavery and caste systems; abandon self and selfishness; and love your neighbour, even your enemy. Many statements by Jesus resembled those by Buddha, as presented below.
JESUS: "A foolish man, which built his house on sand."
BUDDHA: "Perishable is a city built on sand."
JESUS: "Therefore confess your sins one to another, and pray one for another, that you may be healed."
BUDDHA: "Confess before the world the sins you have committed."
JESUS: "In him we have redemption through his blood, the foregiveness of sins."
BUDDHA: "Let all sins that were committed in this world fall on me, that the world may be delivered."
JESUS: "Do to others as you would have them do to you."
BUDDHA: "Consider others as yourself."
JESUS: "If anyone strikes you on the cheek, offer the other also."
BUDDHA: "If anyone should give you a blow with his hand, with a stick, or with a knife, you should abandon all desires and utter no evil words."
JESUS: "Love your enemies, do good to those who hate, bless those who curse you, pray for those who abuse you."
BUDDHA: "Hatreds do not cease in this world by hating, but by love: this is an eternal truth. Overcome anger by love, overcome evil by good."
JESUS: "This is my commandment, that you love one another as I have loved you."
BUDDHA: "Let your thoughts of boundless love pervade the whole world."
JESUS: "Let anyone among you who is without sin be the first to cast a stone at her."
BUDDHA: "Do not look at the faults of others or what others have done or not done; observe what you yourself have done and have not done."
JESUS: "You father in heaven makes his sun rise on the evil and on the good, and sends rain on the righteous and on the unrighteous."
BUDDHA: "The light of the sun and the moon illuminates the whole world, both him who does well and him who does ill, both him who stands high and him who stands low."
JESUS: "If you wish to be perfect, go sell your possessions, and give the money to the poor, and you will have treasure in heaven."
BUDDHA: "The avaricious do not go to heaven, the foolish do not extol charity. The wise one, however, rejoicing in charity, becomes thereby happy in the beyond."
So while a historians like Josephus and Tacitus may refer to a following of a man put to death at the time of Pilate (almost a century after he is supposed to have died); and filtering the gospels canonical and apocryphal points to a lost common source of sayings and biography where the non-conflicting accounts attributed to his life stem from (known as Q); there is no evidence that the document Q is the life of the reported man if indeed he did live.
Back in 1985 in Tibet there was a woman who preached a parable about a knight who was seduced by an evil wizard and killed his fellow knights and made the wizard Emperor but was saved by his son and she was killed by the Chinese.
If a Chinese journalist reported that there was a woman who preached in Tibet and was killed preaching something other than Buddhism there wouldn't be an immediate assumption that she wasn't preaching from the gospel of St Lucas because it's the modern world and we can make these connections more quickly and with greater accuracy.
2000 years ago it become a bit more fuzzy.
The story of Barlaam and Josaphat is definitely pulled right out of the life of Buddha.