The Redstone Plane was merely an inconspicuous Minor Plane. Although intelligent life was rare there, and it possessed a modest human kingdom where people lived and multiplied, none of that changed the fact that it was only a Minor Plane.
A Minor Plane meant scarce resources; a small kingdom meant a sparse population; a remote location meant no contact with the outside world.
When these three shortcomings came together, ridiculous ideas such as ignorance, foolishness, recklessness, and self-importance naturally emerged.
Faith was easily spread on such Minor Planes.
Since the strongest beings on the entire plane were no more than two or three Master Level combat professionals, and the "Legendary tier" existed only in legends and stories, even an unknown god who displayed no miracles could absolutely talk a sizable cult into existence with nothing more than a few priests. There were always far too many ignorant people willing to worship so-called "omnipotent" gods.
However, such Minor Planes also had factors that hindered faith. Having never seen a Legendary powerhouse, and never having even produced a Master Level spellcaster, the intelligent beings raised on such planes lacked reverence for the strong. Even if a god displayed some "miracles" here, the nobles who occupied positions of power would naturally never easily submit to the rule of a god who existed only in legends.
Especially when the church seeking to expand its influence was an outright Evil God cult, whose conduct could fairly be described as indiscriminate slaughter of innocents, its existence was even more difficult for most rulers and "righteous people" to endure.
In fact, it was never easy for a church with doctrines as extremely evil as the Red Sands Cult to take root anywhere orderly. It was not hard to see from the fact that these ten thousand-plus believers