With Chad specifically, the only thing he told his family/the public at meetings was his doomsday prophesies, and most of his family shrugged, shook their heads, and made secret circles around their ears: 'loopy'. A lot of people are into that.
The predictions about Tammy dying, light and dark, zombies, was kept secret from most people. He only stated those things to the true believers in his ability to receive visions of the future, etc.
If you are interested, there are many interviews on Hidden True crime youtube (an approved source), such as with his brother's wife. She felt strongly about his doomsday predictions, but had no idea about how far it all went.
JMO