Jerusalem and Antioch were 2 of the most important of the 5 churches in that area of the world.The Nicean Creed was formulated under the auspices of a pagan emperor who them persecuted and threw out the dissenters. The 'Catholic' church you speak of was in no way universal by the time of the 4th century. It was a name the bishops of Rome held on to to give the impression of originality, but there were earlier churches in existence long before Rome became prominent... Jerusalem, Antioch for example.
The others were: Rome, Constantinople, Alexandria.
All five were the Catholic Church.
If you can find another name, please do so.
This is simple history.
You're right about the arian heresy.The purpose of the Creed was to forge a political unity and unite what remained of the empire under the pretense of spirituality.
Arius, a bishop whose core beliefs only come to us through the writings of those who opposed him, wasn't alone. And his teachings that converted an entire nation, the Ostrogoth, were converted by a missionary named Wulfila whose writings clearly support a non trinitarian mindset, but a pro divine deity of the Son, Jesus. So Catholicism wasn't the only shop in town.
And those Ostrogoths were declared Arian...barbarian... By the power that had them destroyed... The Catholic Church. Which suggests the Trinity debate for many was more about politics than spiritual truth.
The Catholic Church stopped many heresies or we would not be united today.
The Creeds were forged to make known to all what the church believed as doctrine.
This was true of all creeds...they were always to correct a heresy.
This does not make the Trinity political.
It was discussed many years before 325AD.
Do we not have one Goid and one Christ? Is there not one Spirit of grace, poured out upon us?
Clement of Rome 96AD
Clement of Rome was taught by Peter and Paul...mainly by Paul.
The church was not yet political at this time in history.
I have largely demonstrated that the Word, namely the Son, was always with the Father.
Wisdom, who is in Spirit, was present with Him before all creation.
Irenaeus 180AD
Irenaeus was taught by Polycarp, who was taught directly from John.
There's more should you require it.