Factors contributing to the diversity of early Christian groups

Lack of Leadership

The Christian movement spread very quickly and not in an organized way

Followers of Jesus had different expectations of what he would do, and interpreted what happened afterward differently as well

Unless you follow Matthew, the other gospels don't depict Jesus choosing an heir with whom he communicated his core beliefs

It's not like Judaism or the pagan religions of the time were uniform in their ideas either

The destruction of the Temple and the loss of much of the Jewish leadership caused a massive re-evaluation of Judaism, so that made new forms more possible

Lack of Communication

Far flung groups and the difficulty of communication; stories may have developed differently as they spread to new regions

Different cultural groups present from the beginning, causing different understandings of Jesus: especially Jews and non-Jews

Jesus was relatively unknown so there would not have been good documentation about his ideas

Many of the sayings attributed to Jesus are ambiguous and can be interpreted in different ways

Each founding community had their own traditions and did not communicate much with other groups

The cataclysms of the Jewish war and the Roman response to Christianity made calm reflection difficult

Lack of Authortitative Texts

The lack of an agreed upon canon of authentic writings

With no agreed upon text, strong leaders like Paul or Marcion can be very persuasive

Revelation was accorded as much if not more respect than written records

Even if there were written texts, few people could read them

Stories circulated orally for some time and sayings continued to be added