Mensa,
The World Wide Church of God was founded by Herbert W. Amrstrong who was a very strong leader, much like Rutherford. As he got older he attempted to turn the leadership over to his son Garner Ted Armstrong. They had conflict and the son fell out of favor, and Herbert W. took the leadership back. When he died, there was not the successor, like the JWs had with Knorr after Rutherford's death. That is why they changed their doctrines, because they could with no interferring dictator. Their numbers did not remain high, as you assert, but dropped dramaticly. I have a good friend who used to be a member. In fact, he worked at their college for some time. He can update me on the details and the actual numbers. I will also make sure my statements here are accurate, since this is off the top of my head.