Was the Bible really written 300 years after Jesus's death?

 

It was compiled at some point in the mid-4th century. But it was compiled from pre-existing texts – like the entire Old Testament, for example.

Our best estimates say that the Gospels were written over a period of a century or so, starting at about 70 CE. This means that it is possible that the earliest texts had access to eyewitness accounts; it would have been relatively easy to find people in their 60s who had been about 20 during Jesus’ ministry. The Epistles are older: some are pretty much universally regarded as authentic writings by the Apostle Paul, who died around 65 CE, but you should note that he never met Jesus.

In the early 4th century, there were any amount of texts in circulation purporting to be Gospels, and they were usually attributed to one Apostle or other. This was a common literary technique of the time, and was not expected to be taken as factual. The early Christian Church decided to prune them, and finally settled on four – three of them obviously early and fairly down-to-Earth, as religious tracts go, and the fourth (John) bearing some signs of a more Gnostic tradition.

Some of the others were quite out there, and e.g. the Gospel of Barnabas, which had Judas take Jesus’ place on the cross and then Jesus going around continuing to preach for decades, was obviously very difficult to square with the others.