Trinitarians will tell you that the Jews had a fairly well developed concept of the trinity. This is religious insanity.
On the day of Pentecost the Jews looked upon Him whom they had pierced and recalled that God, through Zechariah, had said “Me”.
It’s the Greeks who had to explain it and went to great lengths to repack the incarnation as an inexplicable mystery. Till then, they knew what Jesus said. The father Eternal God was in the son and the Word or expression ( the Son) was made flesh so that infinite God appeared in mortal flesh. The rest is someone else’s pipe dream, with no good motive.
-MB