False Prophet William Miller and The Seventh Day Adventists went on to spawn, in 1955, the Davidian Day Adventists, many of whose members perished in the fiery inferno that ended the infamous Waco Seige of 1993. 

Other groups that would evolve from The Great Disappointment, either directly or indirectly, include The Christadelphians (circa 60,000) , The Church of God Seventh-Day (circa 200,000), The Church of God General Conference (circa 300,000) Church of the Blessed Hope (circa 800) The Seventh Day Adventists Reform Movement (circa 35,000) Davidian Seventh Day Adventists (unknown)  United Seventh Day Adventist (unknown) primitive Advent Church (circa 500) and The Sabbath Rest Advent Church (circa 250). 

Finally, Charles Taze Russell admitted that a presentation by Millerite preacher Jonas Wendell in 1870 (outlining Wendell’s own belief that Christ’s Second Coming would happen between 1873 & 1874) was the direct catalyst for the formation of his Bible Student Movement the same year. 
That group, which later included Millerite writers George Stetson and George Stoors, eventually led to the formation of the Jehovah’s Witnesses in 1931 (approx eight-million)

Was the whole thing a fraud from the beginning...?