Um... there's probably a lot to pick apart there, but for diminishing returns.
You probably already know that the old saying "absence of evidence is not evidence of absence"
That observation can be used on both sides of this particular topic.
Saying that contradicting stories were erased is absolutely realistic, as it definitely occurred, as indicated by the stories about heresies.
What we generally don't have are the works of the so called "heretics" in much volume. What you do have is the reports written later by the church theologians criticizing the heresies but not having the "heretics" own words to check them against. You've probably already heard the term "the victors write history"
And you probably already know that historical evidence is rarely blatant and cut and dried, but has to be examined and interpreted. People in historical documents did not always blatantly write out the information we are looking for.
Anyway, if you are really interested in the arguments made by those who claim Jesus was mythical instead of real, and where they derive their evidence, you could look at this book
Did Jesus Exist ? Now, Bart Ehrman is a mainstream scholar. He is no longer religious himself but once was. In this book he engages the arguments of people who make the mythicist claim. He concludes they are wrong. But at least his book would have some of the information that I THINK you might be looking for.
This book -
Amazon.com: The Case Against The Case For Christ: A New Testament Scholar Refutes the Reverend Lee Strobel: 9781578840052: Robert M Price, Frank R. Zindler: Books It was written by one of the prominent Mythicist scholars, Robert Price.
This book
On the Historicity of Jesus: Why We Might Have Reason for Doubt: Carrier, Richard: 0884967420701: Amazon.com: Books by Richard Carrier, another prominent mythicist.
There's this book, by Thomas Thompson, another mythicist
The Mythic Past: Biblical Archaeology And The Myth Of Israel: Thompson, Thomas L: 9780465006496: Amazon.com: Books
And somebody named Earl Doherty, who wrote this
The Jesus Puzzle: Did Christianity Begin with a Mythical Christ? Challenging the Existence of an Historical Jesus by Earl Doherty (2005-01-01): unknown author: Amazon.com: Books
and has or is affiliated with these websites
THE JESUS PUZZLE - Earl Doherty Earl Doherty: Jesus the Myth, Heavenly Christ
To the point of your question, I guess IF anybody would have found some origin stories that don't seem to lead to a real person, I suppose it would be these mythicist scholars (though mainstream scholars generally do not agree with their conclusions)
That is, IF you are, as I think you are, looking to see what material contemporary to the early Christians would lead to a mythicist interpretation, well, our few modern day scholars that are mythicists would point you in the right direction. They would have looked that stuff up. Problem with all that is, most normal scholars just do not agree with their interpretations of the evidence.