Franz had a clear narrative to follow and was given a lot of leeway. I think he really believed that he was a modern-day prophet, guided by the holy spirit to lead Jehovah's people to the new world.
So, yeah... he was a nutcase. But he was able to promote his specific vision with little or no interference.
Today's GB is driven less by what they want to do and more by external forces and a feeling that they are trying to save the organization from financial decline. They're more worried about marketing. A consistent doctrinal vision is not high on the list.