I feel like you don’t see proper articulation of the Trinity, the incarnation, Jesus having two natures, and a host of commonly accepted positions until you start encountering these Marian traditions, either. As the Church grew and became less persecuted and more accepted and legal, there were more Christians with more resources to write, and a much easier time of preserving the documentation and traditions they had as there was better organizatiin, and the great thinkers got to sit down and consider what they knew and truly contemplate on those things.