You are perfectly entitled to think what you like Spud - but your suggestion flies in the face of the evidence and the vast, vast majority of scholarly opinion on the matter. What we do know for certain is that the NT texts we actually have (extant fragments and manuscripts) are from decades, if not centuries after 70AD.
Why would they - firstly the gospels deal with events from around 4BCE (those that include the nativity) to about 30AD, albeit were written decades later. Why would they slot in events from decades later than the time frame they are supposed to be reporting on.
Acts goes right up to Paul in Rome, around AD 60, and mentions at least one fulfilled prophecy. Matthew mentions several OLd Testament ones. If Acts was written after AD70 it would surely say something about it.
Secondly, is it beyond your understanding that the most compelling way to claim prophecy is to write about a prophecy that you know came to pass while trying to make it appear that you were writing without that knowledge. We see this with Ezekiel - where the book containing the prophecy of the destruction of the first temple was undoubtedly written after that destruction but only talks of the prophecy, not the actual event - the writer leaves the reader to fill in the gaps.
Yes, the book of Ezekiel looks like it was compiled after the events, but how did it become canon scripture if this was false:
"And the Spirit lifted me up and carried me back to Chaldea,b to the exiles in the vision given by the Spirit of God. After the vision had gone up from me, 25I told the exiles everything the LORD had shown me." - Ezekiel 11:24
?
It mentions the fulfillment of the above, too:
"In the twelfth year of our exile, on the fifth day of the tenth month, a fugitive from Jerusalem came to me and reported, “The city has been taken!”" - Ezekiel 33:21
And I think this is the same for the gospels - we know that the texts we have are from way after 70AD so why wouldn't they be edited to include the destruction of the second temple - simple, because to do so would make it obvious that you are claiming a prophecy only after you knew it came to pass, which rather negates the whole point of prophecy.
This depends on knowing the original texts were post-AD70. But you don't know this; there are no references to the fall of Jerusalem that couldn't have been written before the events and based on Old Testament texts.
Eg Luke's "when you see Jerusalem surrounded by armies" (Luke 21:20) and "For the days will come upon you, when your enemies will set up a barricade around you and surround you and hem you in on every side" (Luke 19:43) could be a development of "And I will encamp against you all around, and will besiege you with towers and I will raise siegeworks against you." from Isaiah 29:3.
"They will dash you to the ground, you and the children within your walls. They will not leave one stone on another, because you did not recognize the time of God's coming to you." (Luke 19:44) could be developed from "Therefore because of you, Zion will be plowed like a field, Jerusalem will become a heap of rubble, the temple hill a mound overgrown with thickets." - Micah 3:12.