Where is your evidence for that? The term "Trinity" was originally coined by Tertullian [200 AD] before the Roman Church was organized in the 4th century. And before Tertullian, there was Irenaeus, Hippolytus, Theophilus, Cyprian, and others --- well before the Roman Church. They no more invented the Trinity than they did the Bible, despite their claims.
Rome's organizing in 325-ish was only a formality of cementing apostasies that were already widely held into doctrine. How many of the ECF's that you list above were Hebrew Christians? How many were Hellenizing-friendly Greeks? Your claim that they did not invent the concept of the Trinity is quite valid as it had already existed for over a thousand years.
You, of course, are correct. The Universal Church was not formally organized until 325 A.D. at Nicea. The doctrine of the Trinity was accepted as dogma by this new Imperial State Religion. Later at Constantinople (381 A.D.) the doctrine was made official and complete. In addition to this apostasy the Church began to kill folks in the name of God....those who would not convert or accept this new Trinity Theory.
At the same time other non biblical practices began to emerge from this State Religion such as Mary worship, Penitence, Transubstantiation, Indulgences, Infant Baptism from Jesus' name to the titles Father, Son and Holy Ghost.
The power of this State religion knew no bounds and grew to be the biggest, richest and most influential political movement in the world. Many Churches eventually broke away because of these practices....but yet, kept the false doctrine of the Trinity without questioning it.
So, where did this doctrine come from? It began in Babylon where much apostasy had it's start [Revelation 17:3-5]. It then spread throughout the ancient world. Babylon's Triad was "Nimrod/Father, Tammuz/Son, and Semirimus/Mother". The Triad of Egypt was called "Osiris, Horus, and Isis"; Greece..."Zeus, Apollo and Athena"; India..."Brahma, Vishnu and Shiva"; Rome..."Jupiter, Mars and Venus"; Catholicism..."Father, Son and Holy Ghost".
The Trinity of back slided Israel was called Baal/Father, Tammuz/Son and Ashtoreth/Mother.....and yes, it too came from Babylon.
After the Israelites of the north had been taken captive to Assyria (721 B.C.) for worshiping these same Babylonian Gods the king of Assyria repopulated the north with folks from Babylon....and they became known as Samaritans. [II Kings 17:6] In the ninth year of Hoshea, the king of Assyria captured Samaria and deported the Israelites to Assyria. He settled them in Halah, in Gozan on the Habor River and in the towns of the Medes. (verse 7) All this took place because the Israelites had sinned against the LORD their God, who had brought them up out of Egypt from under the power of Pharaoh king of Egypt. They worshiped other gods.
[II Kings 17:24] The king of Assyria brought people from Babylon, Cuthah, Avva, Hamath and Sepharvaim and settled them in the towns of Samaria to replace the Israelites. They took over Samaria and lived in its towns. (verse 33) They worshiped the LORD, but they also served their own gods in accordance with the customs of the nations from which they had been brought. To this day they persist in their former practices. They neither worship the LORD nor adhere to the decrees and ordinances, the laws and commands that the LORD gave the descendants of Jacob, whom he named Israel.
These folks....the Samaritans of Babylonian extraction, were the same people our Lord cautioned the Apostles about when he said: [Matthew 10:5-6] These twelve Jesus sent out with the following instructions: "Do not go among the Gentiles or enter any town of the Samaritans. Go rather to the lost sheep of Israel."
Simon Magus was a Samaritan....a descendant of Babylonians and we read in [Acts 8:9-11]Now for some time a man named Simon had practiced sorcery in the city and amazed all the people of Samaria. He boasted that he was someone great, and all the people, both high and low, gave him their attention and exclaimed, "This man is the divine power known as the Great Power." They followed him because he had amazed them for a long time with his magic."
Simon was a Trinitarian because he still believed in the religion of his Fathers [II Kings 17:33-34] Simon is mentioned quite frequently by the Church Fathers as being in Rome....supposedly at the same time Peter was to have been there....although this has always been impossible to square with scripture. Simon, after his rejection by Peter, began to fashion his own "Christian" church -- a church of which HE was head -- a church designed to completely overthrow the True Church of God. His idea was to blend together Babylonian teaching with some of the teachings of Christ -- especially to take the name of Christ -- and thus create one universal church! But a church with Babylonianism as its basis. Luke gives in detail the principal character who established the so called Christian counterpart of the Truth in the Apostles’ days. This is the reason the Apostles in their Church letters many times mention the false system as already in existence, but fail to describe its origin. They didn't have to. That was already done right in chapter 8 of Acts....by Luke!
So....Tertullian may have "coined" the word Trinity....but the concept had been around for some time.
[Acts 2:38]Peter replied, "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.