The Gospel Writers Know Their Text Incredibly Well

Each one of the four gospel writers knows their text incredibly well, unbelievably well. How long did john have to live in before he understood the culture well enough towrite this gospel? I mean that would explain alone why the gospels were written when we think they were written aps several decades after christ absoluty. They're not just trying to record quick, let's write it down before we forget. No, they know their audience and their cultural context incredibly well.