The story of King Abgar illustrates the history: but amongst those who actually heard our Lord preach there must have been very many, probably a majority, who were uneducated.

They would easily learn from the Jews, because the Aramaic dialects spoken by Hebrews and Syrians did not greatly differ the one from the other.

What difference there was, would not so much hinder the spread of the stories, as tend to introduce alien forms of speech and synonymous words, and so to hinder absolute accuracy from being maintained.

Much time must necessarily have elapsed, before such familiarity with the genuine accounts of our Lord's sayings and doings grew up, as would prevent mistakes being made and disseminated in telling or in writing.
The Gospels were certainly not written till some thirty years after the Ascension.

More careful examination seems to place them later rather than earlier.