Why not dismiss the trinitarian belief outright

[Foxaèr]

It's always of particular interest that theists unreasonably dismiss the evidence right in front of them while claiming faith in a deity that has zero evidence to support its existence.

[The Grand Nudger]

The short version of a long story, is that the Christianity, and Christian history, that some contemporary Christians have been actively propagandized by is the view of the winning faction. The one that survived.

No more, no less. People have always disagreed on absolutely everything. That was as true of proto christians then as it was of everyone else then, and now.

I respect the fact that a strong belief in the miraculous nature of the narrative and narrative events might lead a person to miss the obvious and argue counterfactually, but it is what it is, and what it was.

As I mentioned to another poster, whatever you believe about a god, or who told the right stories about a god, magic book has a history of its own completely unaffected by those beliefs. Christianity as a historical movement, likewise.

[Fake Messiah]

Finally, you have still not produced any actual evidence that Early Christianity got a Trinity from anywhere.

Yeah, you want a document signed by Christians where they admit how they aped other religions? Or a document signed by Quentin Tarantino in which he admits to aping "City on Fire" (1987) into "Reservoir Dogs" or is it enough to just watch those two movies back to back?

In any case, in this BBC documentary, a certain historian demonstrates how Christianity and paganism are so intertwined that believing in Jesus is like believing in Zeus

[GUBU]

Well, for example, Marcion of Sinope, the inventor of the first christian canon and one of the earliest christians (he lived in the first half of the second century, right at the birth of christianity), believed that there were two gods, an evil one called yhwh who was depicted in the jewish scriptures and a good, hidden, god who sent Yeshua as his messenger.  He also denied that Yeshua had an actual physical body, that what the disciples saw was simply an image.

That's a big disagreement on christian fundamentals from what is now considered canonical.

By 'NT community', I mean the Early Church community portrayed in the NT. All sorts of exciting heresies developed towards the end of C1, but that's not the people I'm talking about. There is no credible evidence that I'm aware of that the community run by the disciples/Paul disagreed on the oneness of God.

As I said above, the first christians appeared in the second century CE. And given that we are basing our ideas on the earliest communities on writings from the 4th century, we actually know very little about them.

[The Grand Nudger]

Most of that, only in the form of other communities which had survived( though may now be extinct) writing against their beliefs.

It was a circular firing squad. Still is. There was, then and now, the belief that particular communities had “gotten it right”, always ones own- and that the others had gotten things wrong. All well and good - but this isn’t actually the same thing as there never having been more than one opinion on an article of faith.

[GUBU]

Most of that, only in the form of other communities which had survived( though may now be extinct) writing against their beliefs.  

It was a circular firing squad.  Still is.

Yeah pretty much anything we know about any pre-3rd century "christian" (and most 3rd century ones) is from 4th century christians pointing out how "wrong" they were, in pretty bellicose and insulting words.

[The Grand Nudger]

My favorite is from a pagan, whose words they immortalized only to argue against. Julian. He gives a pretty good view of how the Roman administrative state viewed Christianity, why they had an issue with it, and even the failures of Rome which lead to its expansion.

He also nails the belief system so simply and so accurately that you could be forgiven for thinking that he was a contemporary critic discussing the state of the faith and its relationship to society today. His mere existence was a near disaster for the faith. Had he not been assassinated there would be no Christianity as we see it today.

[Vicki Q]

OK, so there's no actual evidence that the community described in the NT believed in anything other than God is One. So we can Hitchens that suggestion.

Since we have a Bezos level of wealth of evidence the NT community did believe in the Oneness of God, implicit and explicit evidence, multiple attestations and multiple forms of attestations, given the somewhat obvious (monotheistic) Jewish roots of Xianity, I suggest we move on, and examine the issues raised by the OP.

You'll no doubt be aware of the Shema:

Hear, O Israel: the LORD is our God, the LORD is One

The fiercest expression of monotheism in Judaism, it remains to this day the centrepiece of Jewish prayer. So it's actually a bit of a shock when Paul writes in 1 Cor 8: 4-6

So then, about eating food sacrificed to idols: We know that “An idol is nothing at all in the world” and that “There is no God but one.” For even if there are so-called gods, whether in heaven or on earth (as indeed there are many “gods” and many “lords”), yet for us there is but one God, the Father, from whom all things came and for whom we live; and there is but one Lord, Jesus Christ, through whom all things came and through whom we live.

What Paul has done, in the course of a robust defence of monotheism, is rework the Shema to include Jesus within it. We must have monotheism, but we now have a better understanding from what Jesus has shown us of the nature of God. God is One, but it is appropriate to use Kyrios (Lord) to refer to Jesus, a description used in the Shema of YHWH. This is how the Trinity is best understood; WLCraig's Cerberus probably isn't helpful here (OP).

What is also striking is that Paul doesn't feel the need to argue the point. He goes to great lengths to justify his attitude to Torah, because it's very controversial and splitting the Church. He calls out the personality based factionalism in 1 Corinthians 1. But including Christ within a description of God seems to create no problems and needs no commentary.

Anyway, I would value people's thoughts, although it'll be a week or two before I can respond to them.

[R00tKiT]

Secondly, the NT is clear and non-negotiable on the Oneness of God. In what sense are the groups of three you name one single entity in the same sense?

My ass 

"Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit " (Matthew 28:19 ESV)

"God has sent the Spirit of his Son into our hearts, crying, "Abba! Father!" (Galatians 4:4-7)

Logical equivalence between father and Son : 

All things have been handed over to me by my Father; and no one knows the Son except the Father, and no one knows the Father except the Son and anyone to whom the Son chooses to reveal him" (Matt 11:27)

Jesus is equal to God : 

"For this reason they tried all the more to kill him; not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God." (John 5:18 NIV)

[The Grand Nudger]

You might want to reassess whether you value peoples thoughts, or even the reality of division between proto Christian communities.

You’re simply reasserting counterfactual statements which comport with your pre-existing and demonstrably wrong beliefs about early Christendom.

They didn’t believe what you believe, you think they were wrong- you agree with the surviving faction, instead.