Charles Fillmore was a real estate dealer in Kansas City, lame from a childhood skating accident that had left one leg shorter than the other, and thoroughly unconvinced by the lecture that changed his wife's life. He investigated. He read the mental healing literature, sat in on the classes, and eventually concluded that the thing worked and that he had better find out why, which is a characteristic sequence for him.
What he then built was less a church than a service industry for a teaching. A magazine, Modern Thought, appeared in 1889 and became Unity. A correspondence course followed, then a publishing house, then Daily Word, a devotional booklet that reached a very large circulation, then a campus at what is now Unity Village outside Kansas City. Silent Unity, his wife's prayer ministry, was staffed and organised. Throughout, he insisted that Unity was not a denomination but a way of reading Christianity available to anyone, and that its students should stay in whatever church they already had.
That position became harder to hold as ministers were trained and congregations chartered, and Unity today functions as a denomination while continuing to describe itself in the older terms. The tension is inherited directly from him.