Right up front, some of these guys are making a good point. To read the text through the lens of later theological developments winds up ignoring what the text is actually saying. So in some sense, they are (at least on the surface level) trying to be faithful to the reading of the text as it stands.
But some of them go further: the text, they conclude, doesn’t contain any of those things that later theologians noticed. Some are quick to add some note about the importance of tradition but they do so to point out what they see as a deficiency in relying on Scripture as ones ultimate guide.
In so doing they suggest, without being explicit, that these doctrines originated in a vacuum filled only by necessity. A teaching arose, a response had to be formulated, a doctrine was created. But, it wasn’t Christ’s Deity ex nihilo and I think history proves that. The teaching arose and was recognized as aberrant exactly because there was something substantial already in place.
If you recall, the council of Nicaea was in 325 AD. But jumping solely to Nicaea leaves one ignoring years choc-full of declaring Christ as the Divine God.
So here’s a sampling of early church writings I’ve found that underscored the understanding that Christ is God.