I first became acquainted with the survivalist movement in the late 60s, through my ex-wife’s family, all of which were Mormons. One cousin in Ogden seemed to be on first name basis with several of the camp founders.
The non-mormons came along later around 1974 or so, as the movement gained notariety through news accounts.
I figured you were describing your own personal experience and making it sound like a fact, but really I was looking for something more to back up your claim.
I believe that of course some Mormons would have been part of the movement in the 70s, but I don’t buy your claim.