Bereal - According to who?
Any historian who isn't terrified of being blackballed for speaking out against the idea that Jesus lived.
Here is how professional historians are supposed to work. It's basically the historian version of the scientific method. You find primary sources. Primary sources are essentially first hand, contemporaneous accounts of something. Primary source of the battle of gettysburg, would be someone who fought in, or observed it. To create a historical concensus about something, you typically gather lots of primary sources regarding a topic, and then sift through them. Oh, this guy was a confederate soldier at Gettysburg? Ok, well we should note that he was a confederate when we evaluate this source, because there could be bias. Oh this guy was Union? Same thing. Then you cross examine each and every individual source with every other source. You look for contradictions, you look for concensus.
Jesus? There is exactly ZERO primary source evidence for the existence of Jesus. ZERO. The nearest people to write about him, occured 1 generation after he was supposed to have lived. There are no records or mentions of him in Roman history from contemporaneous sources.
Modern historians basically suspend their own value system when it comes to Jesus. People accept that he was a real person, without actually subjecting his existence to the level of scrutiny any other historical figure/person/event would face.
I suspect, that most historians that are not personally invested in the abrahamic religions, secretly have their own questions about it. However, if you're a historian, or a professor at say Harvard, if you were to publically express those doubts, you'd lose your job.
I'm not saying Jesus wasn't a historical person, what I am saying is, there is absolutely zero fucking non-biased source material that can verify his existence when he was alive. The only source material, is secondary and tertiary, written after the fact, when his existence was already sworn on by the people who were creating the religion and taken for granted by the population at large. For such an important individual, there should be, SHOULD be, some actual contemporaneous references to him. The bible doesn't count, nor was it written when he was alive. It's not a legitimate source for this.