Or the Gospel authors exaggerated the witnesses and events or fabricated everything.
1) Can you prove that
2) If they had fabricated everything they would have been very easy to dispute.
Easy example;
Governor Quirinius of Syria wasn't governor when Jesus was born, and the census he carried out did not require people to go back to the place where their ancestor 1000 years ago was born. Apart from the Gospel of Luke, there are zero accounts of people having to travel for a census at the time, but plenty of accounts of that governor carrying out a census.
Just think about it; 1000 years is about 40 generations. That would mean you would have 80 different great great etc. grandparents born 1000 years ago. How do you decide which one is the one whose birthplace you have to go to? Why would you have to go there? How would any businesses, food production, law enforcement etc. still be carried out? Why would nobody other than Luke write about it?
The only
rational explanation is that Luke made up that story so that he could make up a reason for Jesus to be born in Bethlehem, as predicted by the old testament. If Jesus wasn't born in Bethlehem then the prediction of the Old testament that the messiah would be born there is incorrect, and because religious people are dishonest, Luke lied in order to convince people that what he was saying was true.