Sure, one can doubt anything, but lets consider something quickly.
There was people who knew Jesus, they were apostles and disciples.
They wrote what they knew about him.
They went around the Jewish world, preached in synagogues, and made many Jews to accept Jesus as their Messiah.
These people also knew Jesus, or there was a lot of people who knew him, and remembered when He taught in their villages, and if these Apostles and Disciples would have concocted lies, they would have been corrected and such scriptures would have survived.
Therefore, by pure peer observation, it is highly impropable that Jesus never existed, and totally propable that the reason why these apostles gave their lives in believing that Jesus was ressurrected from the dead, and that He did exist.
Furthermore, it was the same first Christians who collected the writings about Jesus, and their desacendends who kept it safe during 300 years of persecution that gave us the NT.
people such as Polycarp, who knew John well, certainly would not have given his life by burning, if he thought there was a scant hint of corruption in the history of Jesus and the apostles.
I would like to continue, but it is time to go home now.