Sooo....
Say a group of local believers decides to pool their resources and build a fellowship hall. Everything is hunkey-dorey.
Then two of the group's members disagree with each other over some point of doctrine. Perhaps one says there was an Aramaic substrate, and another contends that the original autographs were in Greek. Neither one can understand why the other is being so pig-headed and obtuse. Their disagreement flares throughout the group, and soon there are two camps who cannot stand the sight of each other, much less sharing the same fellowship hall.
They decide to split. Which group gets to keep the hall? After all, it was a substantial investment.
They go down to the courthouse and ask a judge to decide. The judge thinks the New Testament was originally composed in King James English. The judge is going to flip a coin to make the decision, but the leader of the Greek autograph faction convinces the judge his group will be able to campaign more effectively for the judge during the upcoming election than the Aramaic faction will. So the judge decides that the Greek autograph faction gets to keep the building. All of the other leaders of groups that own fellowship halls in the town start teaching the Greek autograph position, because they don't want to lose their buildings.
That's why Theodosius declared the Nicean position to be orthodox, and anybody who held differently to be a deranged, insane heretic.
That's why "Their meeting places shall not receive the name of churches" (be eligible to receive a subsidy, or in our culture, they would lose their tax-exempt status).
Before the late fourth century, it was simply assumed that if a person became a Christian, that is, if a person received baptism, then that person was saved and his immortal soul would automatically go to heaven when he died. When Theodosius said Christians who disagreed with him would "be smitten... with Divine Vengence", he was declaring that Christians would be sent to Hell eternally on his say so.
The Roman legal system had no provisions for dealing with differences of opinion (the original meaning of the word "heresy"), so the magistrates had to resort to laws regarding maleficium (cursing through sorcerous means) to enforce orthodoxy. Theological disagreements turned into literal "witch-hunts".
Love,
Steve