Hi Cofty,
You ask whether there was a person named "Jesus" (actually "Joshua"/Yeshua).
Perhaps we should ask whether the significance of Jesus is the outcome of the creative imaginings of one person - Apostle Paul. His followers decided which writings were scripture and it is no surprise that his writings dominate, including those gospels which show their allegiance to Paul. Many say that Paul invented Christianity, but I feel that this might be a stretch too far, inasmuch as Paul was persecuting Jews in Damascus who were aligned to the Jewish sect of "Jesus" (Yeshua).
Nevertheless, inasmuch as Paul's writings are the earliest, his inventive ideas on matters such as baptism and the eucharist are fundamental to subsequent Christianity,
The person who provides the significant interpretation of Paul is a Benedictine Monk of the 11th century named Anselm. Now, I could be quite wrong here (not the first or last time), but my understanding is that for Augustine, salvation related to the group. In other words, God was saving Israel as a nation. My understanding is that Anselm turned that idea on its head and said that salvation relates to the individual. Hence his ideas align with subsequent Protestantism. I say this with the caution that my current understanding needs some intense research and thinking.
Doug