The first of your assertion concerning early Christians is not correct. They did believe Jesus was God.
Did the Earliest Christians Really Think Jesus Was God? One Important Example
December 11, 2014
Are you serious? Writings from the second or third century??? The "weeds" had well and truly established themselves by then.
Did you not know that the foretold apostasy was already snapping at the heels of the apostles whilst they were still alive in the first century? With the death of the last apostle John, the Bible's canon was closed....and for very good reason. The foretold "weeds" sown by the devil were going to subvert Christianity in exactly the same way as Judaism before it was also corrupted. The trinity is a product of the apostasy.....it was never a teaching of Jesus.
The first Christians had no trinity because Jesus and the apostles were Jewish, and would never thought to teach such blasphemy.
And that's not an accurate description of the second Adam at all.
1 Corinthians 15:“
since death came through a man, the resurrection of the dead also comes through a man. For as in Adam all die, so in Christ all will be made alive” (verses 22-23)."
Source and more reading:
Why is Jesus called the second Adam? | Biblword.net
I would challenge your source on the interpretation of those verses.
The principle applied to Jesus' sacrifice is a well known one.
God's law required "an eye for an eye, a tooth for a tooth, a life for a life". This denotes equivalency. The life Adam lost for all his children was the perfect, sinless life that God gave him. He paid for his own sin with his own life, but there was no one to give a ransom for the perfect life lost for Adams "many" children. (Romans 5:12)
The "last Adam" was the exact equivalent of the first Adam. He was not half man-half God.
Jesus volunteered to come to earth and give a perfect human life to redeem those "many" who had lost it through no fault on their part. He did not have to be God in order to do that. He just had to be the sinless equivalent of the first Adam.
And because Yahweh is one God and not three, (Deuteronomy 6:4) and he was an immortal God who cannot die, Jesus could not be God himself. He is what he said he was "the son of God"....nowhere is he called "God the Son"....nowhere is there "God the Holy Spirit" either.
Who did Jesus pray to and why did he need to if he remained God in the flesh? How could God know things that Jesus didn't if both are God? When you take the trinity apart.....you see it is satanic nonsense designed to make people offend their God unwittingly. Blasphemy in the OT was punishable by death.
This is why those Christ rejects at the judgment are shocked to find that their "Christianity" was nothing of the sort. (Matthew 7:21-23)