Why non Muslim Historian cannot find much about Mohammad or Islam?

How many ancient Historians mentioned Mohammad?
Update: @ think Tanker...
What does Christianity has to do with this?
There is the same problem with Christianity; there is only ONE eye witness Historian.
Jeze! why do you guys turn every question into a religious war?
Update 2: @ lemon Tea...
This has nothing to do wth Christian Historians.
Remember, the only eyewittness rocords of Mohammad was made by Christians.
Christian Historians have also have found very little about Jesus.
So why the confusion; just answer the question...please.
Update 3: @ Susan. I never said that he did not exist but if there are stamps and letters; where can I see them?
Can we dig up his grave to see his holy bones?
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