Around the Mediterranean in pre-christian times triads of gods were common and a part of Egyptian, Etruscan, etc., religions and the converts weren't always asked to give up their pagan beliefs. But no problem according to John Henry Newman in his famous essay on doctrine,
“....the rulers of the Church from early times were prepared, should the occasion arise, to adopt, to imitate, or sanction the existing rites and customs of the populace, as well as the philosophy of the educated class.”
Note well that last sentence.
As Paul noted, some of the future “kings” wanted to begin ruling right immediately, the inroads of false teachings making inroads even then.
Continuing from John Henry Newman, "St. Gregory Thaumaturgus supplies the first instance on record of this economy. He was the Apostle of Pontus, and one of his methods for governing an untoward population is thus related by St. Gregory of Nyssa."
Gregory Thaumaturgus was born in the 3rd Century, and thus a contemporary of Origen, and after the first generation of teachers I mentioned earlier. So evidence of this adoption is not seen until the 3rd Century AD.
You have not be able to show a Platonic influence on the early church fathers at the time immediately after the Apostles, and you have a qualified agreement that some early teacher taught the Trinity. I have presented evidence from multiple sources that stated that the church father after the Apostles taught the trinity.
Therefore, did they teach in error, or did they teach what they were taught by the Apostles?