I don't think that there was a "written word" called the bible for about 400 years after Paul was dead. All early christianity was indeed by word of mouth and tradition. The Catholic Church compiled, edited transcribed, and protected the teachings now found in the printed version. Until the 1400's when Gutenberg provided a method for the average person to possess a bible, only the very elite or royalty or libraries even had a copy because they were expensive hand written versions. Word of mouth and tradition were the only tools available to the early church.
No written word before 400 years after you say! Wonder what Peter would say to that?
2 Peter 3:15 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you; 16 As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
If nothing was considered the “written word” prior to “400 years after Paul was dead”? Did Paul then write them after he was dead? Or are you saying that the CC wrote stuff and claimed it was the apostles.