After the beheading of James (AD 44) the church in Jerusalem got Mark to interview Peter and write down all he could remember. And that was preserved as the gospel of Mark. Matthew had written down logia that he heard verbatim from Jesus, so he spliced this into ninety per cent of what he found written in Mark's Gospel and began his Gospel with what he had heard from Mary. Paul read Mark's Gospel while under house arrest in Caesarea, and he sent Luke to use it as a framework for careful research based on interviewing Mary, people in Nazareth, and other apostles. This careful work introduces his Gospel. (Luke 1:1-3) We can then see why John would want to omit all that Matthew, Mark, and Luke had already made available and focus in his gospel on what he had learned as the beloved disciple.
The advantage of this model is that it is based on believable live individuals
that we know and can picture doing exactly this in the period between 44
and 66 AD.