Yes is was! And this persecution diminished with the conversion of the emperor. Still, we know from the Scripture of Revelations (and other Scriptures) that serious and destructive division existed already.
So the Church existed and was sustained before Constantine even with division, and the Church existed even with division after Constantine. However, the liberty from legal persecution allowed a positive growth by communication through the legalization of Christianity by Constantine.
Constantine gathered the Christian leaders to allow universal teachings and Church law to be established, made known, and convict believers.
Constantine had a certain authority which Christians are called to submit to (as Peter Taught us). Even as Herod had authority to assemble all the priests and demand an answer.
Matthew 2
When Herod the king heard this, he was troubled, and all Jerusalem with him;*and assembling all the chief priests and scribes of the people, he inquired of them where the Christ was to be born.*They told him, “In Bethlehem of Judea; for so it is written by the prophet:
*‘And you, O Bethlehem, in the land of Judah,
are by no means least among the rulers of Judah;
for from you shall come a ruler
who will govern my people Israel.’”
It begs the question: What if all Christian leaders were assembled today. Who would come, what would be decreed, and how would all consent?