Why the first xians didn't believe in the resurrection of Jebus

Considering how important the resurrection of jebus is to xians it gets mentioned once in the whole bible. That being the end of mark's gospel. But it gets worse for them. The end of mark's gospel is considered to be a fake. So basically nowhere in the bible did it say that jebus rose from the dead. No only is there no evidence for the resurrection but their bible doesn't even teach about it.