Luther, Calvin, Zwingli, and the other reformers challenged papal authority, indulgences, works-based salvation, and the corruption of Rome. But not one of the major reformers touched the Trinity. It was inherited wholesale from Catholic theology and passed directly into Protestant doctrine. The creeds remained. The Greek framework remained. The Reformation corrected many things — but it handed every subsequent denomination a trinitarian foundation that no one examined. Modern Christianity inherited what the reformers refused to question.
The Reformation — The Trinity Goes Unquestioned
Luther, Calvin, and the reformers challenged Rome on many things — but inherited the Trinity wholesale without examination.