Trinity theology shows a slip in adherence to truth in the emerging world of Christendom. The slip was happening in how divinity was being understood in a world combining Greek and Roman thinking with newer Christian teachings. There was truth which lay in the real oral tradition humans had of divinity; truth relied on by the disciples of Jesus in their understanding of him. Gods are not human but were called divine, totally divine. Greeks and Romans taught of some exceptions where divinity is not 100% with some kinds of being, such as demigods and heroes such as Hercules. However, humans too can have some measure of divinity without ceasing to be human. One typical oral tradition of this through history has been the concept of chosen, also combined with high nobility such as royalty. Here the character of a human, though not negating their humanity, shares qualities of character normally associated with the non-human gods. Early tales manifest human oral understanding of this and add detail to it, such as Gilgamesh despite being supposed half god, still could not stay awake for seven nights, exposing his lack of full divinity. Jesus in his time and the immediate century or so after his time, he never claimed full divinity, and in fact a denial of his utter humanness was a mark of thinking of a spirit of antichrist. Rather, Jesus is shown as having some qualities of divinity to a higher degree than others around him, even his disciples, and this singles him out as chosen, as the Christ, a similar concept to divinely ordained royalty, but the epitome of it. Recognition of him as the Christ is understanding that he is fully human and his divinity is something akin to that of a king, or a prince chosen to be a king, by virtue of possession of divinely noble qualities, or that these qualities are a manifestation of the truth of having been chosen. It was clearly understood that he was not God Himself. That went without saying. (Arguably, if Jesus or his disciples had ever claimed Jesus to be actually God, it would have probably caused even the closest disciples to abandon him and agree with the Jews about their charges of blasphemy.) For example, in the gospel Jesus is recorded as having stayed awake in Gethsemane while his closest disciples could not do so. This does not make him God in the fullest sense of divinity devoid of humanness, since he is shown another time sleeping in a boat in a storm, whereas God Himself never sleeps. To qualify this, Jesus did teach about himself having preexistence. Yet the disciples (as Peter wrote in one of his epistles) understood his meaning to be his preexisting spirit of his chosenness, the Spirit of the Christ, which inspired prophets before he came, and is found clearly expressed in writings such as the Book of Enoch. Enoch wrote of a Son of Man as if he existed even before the Flood. David wrote of “my lord” as though he already existed. This was known to the disciples and they recorded that Jesus clarified it all to them, but it did not change their understanding of him being a human yet chosen by God to be the Christ.
Possibly in later centuries the details of this understanding got lost and the course grained understanding remaining among Christians was one of Jesus being God, like the Father is God, which of course would in the time immediately following the time of Jesus, have been seen as serious error on a par with antichrist spirit, denying his humanness and chosen nature as the Christ. Divinity clearly, over the decades, changed its meaning when applied to Jesus. Hence came the Trinity developments of theology, partly because these changes in understanding had started to clash with Jewish formalisations of strict monotheism.
Now, comes the important revelation of the time of Jesus himself and the apostles. It was that added to this understanding of Jesus was that the divine qualities seen in him were not merely generic god attributes, but those of one God in particular, the Father.