Allow me to clarify. Beliefs that were later termed "orthodox" did exist prior to Constantine. They were one thread of many Christianities. Only in retrospect can these beliefs -- as they existed pre-Nicea -- be called "orthodox".
that one needs to similarly point to 325 as the year that Jesus became God.
Which is precisely the assertion -- somewhat tongue in cheek -- I made last week. Before 325, some Christians believed that Jesus was God, but many did not. It was Nicea that established this belief as orthodox doctrine.
I think we understand each other.
At Niceae these orthodox things were defined. And, afterward, the Emperor put the muscle behind these teachings. (Whether this is good or bad if another subject.)
To see this as the beginning of something new is to hold a view that the Catholic Church is not the bishops who got together and hammered out what was orthodox, but rather the force of the state in eliminating heterodoxy.
The latter started after Nicea. I don't see how one can say the former did.
And they are not, by necessity, one and the same.
SD