It’s probably reasonable to presume that that no one at that time even had the notion that other writings would become canon or think that anything like a New Testament would come into existence.

The gospels weren’t even all written yet, after all.

The writer would have had no way to presume his own words were inspired by God and in fact made no claims that they were.

In fact, the church councils that decided matters of canon over the next few centuries made lots of contradictory decisions, some of which were even reconciled by violence as bishops attended with gladiatorial escorts to try to influence or force votes.

The idea that God had a hand in these councils is pretty hard to swallow, maybe as hard to swallow as the idea he inspired violence in Old Testament times.

Sola scriptura seems to rest on a foundation of air. It requires continuing revelation while it denies continuing revelation.

The snake eats its own tail.