Was the Council of Nicaea (325 CE) a scriptural or political decision?

In 325 CE, Emperor Constantine — not yet baptized — convened bishops in Nicaea. He called it, funded it, hosted it, and presided. The key word homoousios (same substance) does not appear in scripture. Dissenters were immediately exiled. Constantine was later baptized by an Arian bishop. The New Catholic Encyclopedia calls the Trinity "a late 4th-century invention." Encyclopaedia Britannica: "Neither the word Trinity nor the doctrine appears in the NT." Should the decisions of a politically-driven council define Christian doctrine? How does Acts 17:11 apply? nwtprogress.com