Mormon clarifies the religious issues among the Zoramites. The very first is that they had previously had the word of God (the Nephite religion) preached to them. They were not sinning in ignorance, but rather had intentionally left the Nephite religion.
In addition to leaving Nephite theology, they had left the law of Moses. This makes the Zoramite apostasy different from other Nephite apostasies such as Nehorism. Where that apostasy removed the Messiah but retained the law of Moses, the Zoramite apostasy removed both. They were not just apostate, but they were really apostate.
In such a dramatic state of religious separation from the Nephites, it is not surprising that it was assumed that a political separation was imminent. Religion and politics were not completely separable in the ancient world where one might rule only according to God’s will and support. This reiterates the fear expressed in verse 4, that “the Zoramites would enter into a correspondence with the Lamanites.”