This is true of Abraham and Moses. It is also true of Jesus. The fact is that you can find parallel myths and real history that existed prior to the time that the bibles were written, and these myths seem to always get to be part of the biblical figures real life story.
Many mythological stories seem to be part of the stories, but in the case of Jesus, the connection to Osiris-Dionysus is very apparent.
Much of the myth of Moses seems to parallel the real life of Hammurabi.
The Old Testament, the New Testament, and the Koran have one big thing in common. They were each written at least 100 years "after the fact," and there exists no contemporary evidence of the main players (other than the OT in regards to around 750-450 BC).
The evidence, in fact, proves the Exodus couldn't have happened. Watch The Bible Unearthed series here, if you haven't already.
As for Jesus, there wasn't a word mentioned about him until Josephus noticed Christians (his followers), 50 years "after the fact." No Greek, Jewish, or Roman historian wrote about Jesus from 1-50 AD.
My "theory" is that Jesus was invented by Paul or someone like Paul in a dream. There were many Christian like cults around at that time, and the Jews were on the verge of getting their asses kicked out by the Romans, so their God was not doing the trick for them.
Over a few decades, Jesus morphed into a real person with a family and friends, all of whom were not around to confirm it by the time this happened.
Again, I'll refer my readers to this article by Scott Bidstrup regarding real history and the birth of Christianity.
Why is a myth easier to believe in? Simple. Since there have been no supernatural acts recorded since the bibles were written, and especially in our information age, where almost everyone has a camera that can record such an event if it happened, one can conclude that supernatural events don't happen.
By inventing (and not on purpose either) people who have supernatural powers and those around these people years after these events supposedly occurred, you basically eliminate all witnesses, which means that no one can say the stories didn't actually happen.
OK, so what about Mohammed aka Mohammad aka Mo aka Muhammed, etc., etc.?
You have to understand that I assumed Jesus and Moses were historical figures until I hit the age of 41 or 42 when Mel Gibson announced he was doing a movie called the Passion. I started out doing Google searches to try to find out what Jesus looked like. What I found was astonishing. Not only was there nothing but speculation as to what Jesus looked like, there were a tremendous amount of Google matches that led me to sites that doubted Jesus existed period. And these sites made fantastic and logical points.
History isn't my number one forte. I still took the historical Mohammed for granted.
I always thought that the conquests began as soon as Mo got out of his cave and spread his word (apparently, not the case).
A discussion at Kafir Girl's blog where Mohammed's existence was doubted got my interest. I decided to go on a Google rampage.
I always wondered what the pre-Muslims predominantly believed in. Apparently most believed in the Sun God or some variation of it. Hello Hammurabi.
By the time Mohammed supposedly lived, the middle east was full of New Testament and Old Testament stories, where Christians were looking for converts, and so were Jews:
From the 4th century AD, Christian bishops made notable conversions of the Kings of Himyar , Aksum and of Ethiopia generally. Narjan, an ancient pagan pilgrimage spot in a fertile valley on the trade route became a Christian stronghold. Medina became a centre of Jewish influence. Christianity and Judaism entered into competition in Arabia, encouraged by the Persians. In 522, King Dhu Nawas Yusaf "Lord of Curls" became the last elected Himyar king, descendent of a Jewish hero, who made war on the Christians. He offered the citizens of Naryan the choice of Jewry or death. When they refused he burned them all in a great trench. Afterwards Narjan as named "the trench". In response the Ethiopians overcame them and Abraha made San'a a Christian pilgrimage point which rivalled Mecca. This led to an expeditionary force of Christians to try to destroy the Ka'aba. In turn Persia invaded and for a short time the country became a Persian satrapy. This confused situation laid the seeds for the emergence of Islam.
When exactly the Arabs started actually buying into the bull that they were descended from the illegitimate son of Abraham and his concubine lover is a bit of a mystery, but I can see where this belief would lead to animosity towards the Jews, and I can also see how the writer of the Quran aka Koran would do his darnedest to spin the Arab bloodline in as positive a way as possible.
But the reality is the Mohammed supposedly had quite a few supernatural experiences, and no contemporary evidence of these experiences exist.
Many historians believe that it took 100 years after caveman Mo's supposed death, for the Koran was written. And there is no contemporary evidence (evidence during the time of Mo's supposed lifetime) which mentions Mo in any way shape or form. It took at least 13 years after his alleged death for that to happen. This leads me to believe that Mo was most likely a fictional person as well.
Here is a video that goes into detail regarding the questioning of whether Mo existed or not: