I think that the fact that reading and writing at that period in time(biblical times) was not such a common thing for people to do and the fact the the majority of the bibical texts(the christian at least) were recording a long long time after the fact. Ever heard of a thing called a tall tale. Now i'm not saying that they are all lies but it would have been very easy for the generations of people passing the stories down to alter them slightly each time. Civil war accounts were documented as they occurred and copied many many times. That is the difference between the bibical and the historical thing.