Did the early Christian communities apply Jesus's teaching to the problems they faced or alter the facts to fit their agendas?

Considering the question of whether belief in God lacks the evidence to support it - and why arguments on their own are not enough.

This video describes the discovery of the earliest copy of part of John's Gospel, the 'John Rylands Fragment'.

Were the Gospel accounts corrupted as they were passed on? Was there any way to prevent this happening?