the thing is the first gospel was only written some 20-30 years after jesus was crucified. people seem to forget that there were PEOPLE around. he had thousands of followers according to the bible at least and there's plenty of evidence for CHRISTIANS at that time (nero). jesus' existence wouldn't have been questioned only 30 years after, it's pretty weird to question if at least a jesus FIGURE existed for this reason.
i brought this up with one of my lecturers when he criticised the census story of jesus (why would you need to return to your place of birth for a census??), that if something huge like that didn't happen then why would anyone believe it 60 years later, and he looked a little astonished and said 'that's a very interesting point' and i was pretty chuffed. the bible isn't evidence of god but as far as a lot of stuff goes it'd be fairly ridiculous for so many people to use a book that says stuff that patently doesn't happen at that time, AT THAT TIME.
you can start a religion based on false facts. Look at scientology.
Sixty years later is a pretty long time, especially back then. The average person didn't live more than 30 years, so that's at least two generations. Without anyone to verify jesus's existence, and people more than willing to believe whatever their priests told them, it wouldn't be that hard to get people to believe in a guy who never existed.
Still though, it's all dated decades later. You would think that if such a GREAT guy existed, and he had THOUSANDS of followers, that some texts from around that time would have been written. And all of this is, as you put it, according to the bible. The bible is not a verifiable source without others to back it up. Considering all of the other ridiculous stories in it, such as a talking bush, a guy who loses all of his magical powers when his hair gets cut, and the entire genesis portion, it's perfectly reasonable for anyone to question the validity of the story of Jesus.