Thought the article says the council 'settled' christology, it still took hundreds of years before it was popularly resolved: for, at least, the first 500 years of christianity jesus was widely regarded as something more like a demigod. This fairly clearly what Paul thought; with Luke likely believing just in a messianic role. Early christianity is perhaps best seen as greeking of judaism: god the father is zeus, the…
That particular Council affirmed that Christianity's God is triune by expressly rejecting Arianism. God sending God to do things God could already do is heavily a consequence of the trinity [2], hence why Nicaea was a big deal theologically.
Whether a monotheistic God is unary, binary, trinary, etc has implications that seem sufficiently fundamental that no major religion will abandon its chosen view.