There are also many other "gospels" and other early Christian texts which were purposely left out of the New Testament by the people who put it together.

People at the time of Jesus had varying views on what Jesus was all about and a sort of synthesis was developed to create an "official" religion out of it. Christianity as it it now actually formed more out of Paul's view on Christianity than from Jesus's direct disciples. Paul even talks in his writing in the new testament about how he confronted Peter somewhere and spoke against him (even though Jesus himself appointed Peter as the foundation of his church).

After Jesus's death, the disciples were in Jerusalem in the midst of the termoil of the Jewish rebellion, while Paul was off away from all the chaos where he could go around preaching. Paul supposedly never actually even met Jesus, or at the least, he spent a lot less time with him than the disciples would have.

There are still documents existing written by those who were deciding what texts would form the official new testament, and what their reasoning was and why they chose what they chose.

The form of Christianity and the predominant texts that emerged is a result of many factors, including Roman political ones.

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