The fall of the Church is best illustrated by repeated stories like this one. It takes place not long after Nicea, somewhere around A.D. 330, while Constantine the Great was still emperor of Rome.
Eusebius of Nicomedia (not the historian, though from the same time period), having been readmitted to the empire upon his repentance, nonetheless maintained an ongoing battle with Athanasius of Alexandria over the subject of the Trinity.
You would think this would merely result in arguments, but during the fall of the Church the bishops were too involved in government for that to be the case.
During the time that Constantine was trying to restore Arius to the fellowship of the Alexandrian church, Athanasius, then bishop of Alexandria, refused Arius readmittance, as Arius had not repented.
This frustrated Eusebius of Nicomedia, who apparently saw this as a way to return to the Arian ways that he had rejected after Nicea. Socrates testifies that Eusebius and others made numerous attempts to defame Athanasius and have him removed from leadership.
The following is perhaps the most inisidious.
Eusebius' faction gained hold, somehow, of a human hand. They declared publicly that this was the hand of one Arsenius, a Melitian bishop, and that Athanasius had been using it to perform magic rites.
The fall of the church was in full swing.
When Constantine heard of this he ordered Athanasius brought before him. He also declared that Eusebius and his friend Theognis, the other bishop who refused to sign the Nicene Creed, should be present at the trial.
When Athanasius heard about this, he sent scouts all over Egypt to find the mysterious Arsenius, whom he had supposedly murdered. He was able to find that he existed and was alive, but he was not able to have him brought to Antioch, where the trial was to be held.
When, due to his travels, Constantine ordered the trial moved to Tyre, Arsenius could not resist. He went to Tyre to see what would happen. Socrates called this "the special providence of God."
The servants of Archelaus, the governor of that province, heard some rumors from a nearby inn that Arsenius was not only alive, but present in the area, and they informed the governor. He immediately arranged for a careful search and found and captured Arsenius.
Rather than expose the fraud immediately, the governor decided to have some fun.
(Note: fun for him; for us, we should be mourning over the fall of the church and that "Christians" could behave like this.)
Athanasius was brought before synod to be tried, and they quickly produced the hand and pressed their charges.
Athanasius was ready. He repeatedly asked his questioners whether they actually knew this Arsenius. When several said they did, Athanasius had him brought in.
It was an act of great drama. Arsenius was brought in with his hands covered by a cloak.
Athanasius asked, "Is this the man who has lost a hand?"
As it turns out, very few of those present actually knew this was a setup. The rest assumed the accusation was quite true, and they were astonished that Athanasius was bringing his victim into the courtroom.
Athanasius played the drama perfectly. First he lifted the cloak from one hand.
Then he waited.
Some in the room were still quite certain that Arsenius' other hand was the missing one. Athanasius let the tension build.
Finally, completing his drama, he exposed Arsenius second hand and announced, "Arsenius, as you can see, has two hands. Let my accusers show us the place from which the third was cut off!"
This is a delightful story—if rather grotesque—but it unfortunately illustrates the fall of the church after Nicea. Constantine's "deliverance" of Christians from persecution was perhaps not a deliverance but an overthrow of Christianity.