Within seventy years is not contemporaneous.. It is not even close. If half of the Jesus stories were true one would expect at least some contemporaneous mention of him.
So we're back to "If God doesn't do what SZ expects," which subverts "God is a god of miracle surprises" as it is... sigh.
The NT authors kept transmitting stories orally, building converts, and as mortality neared, got scribal help to transmit their stories for posterity. Does that help?
Again (and again and again and again and again) I've also suggested that no one with living memory within the 70 years or FAR less for early NT docs wrote a counter claim of any kind. You've never once responded to that!
Where is the rabbi or Roman who writes, "The hated Christians are now in the thousands, claiming the Jewish Law is unneeded due to their mythical figure. I lived in Jerusalem and Yeshua of Nazareth never traveled the length and breadth of Israel for years, healing thousands or rising from the dead!"
Same argument from opposing sides, argument for the absent of textual evidence. If one dismissed another's argument, then their same argument must also be dismissed.