Support for Flat Earth within the Firmament was accepted by nearly all Church Fathers who addressed this issue, so what you say does not make sense. Do you have factual source? Or is this simply your own speculation erroneously stated as fact?
Here is what AI says about early Christian history:
"the early Christian scholarly tradition was not defined by a belief in a flat Earth. The consensus among the educated was to accept the spherical model, with debates focusing more on its theological implications (like the antipodes) than on its geometric reality. The flat Earth myth became widespread much later as a tool to portray medieval Christianity as opposed to scientific progress."
Venerable Bede, Doctor of the Church, wrote this in the early 8th century:
"We call the earth a sphere, not because the circle of the circuмference is equally round in all directions, but because, by the compresence of all its parts, it is gathered into the shape of a sphere. Hence, it is that the stars of the northern hemisphere are not visible to the inhabitants of the southern, and conversely, those which are familiar to the southerners are unknown to the northerners."