Most "cults" I've read about (defined as a new social movement based on a shared, novel world view) derive their vitality and staying power from their ability to attract female converts. We see that in early Mormonism, for example, which explains the male founders' ability in the 19th Century to build large families with plural wives. Considering the social standards these women challenged -- joining a controversial religious movement AND defying traditional beliefs about marriage and adultery -- their dedication seems all the more impressive.
Apparently the organized Ayn Rand cultism in the 1960's (the Nathaniel Branden Institute) also attracted a lot of women. From what I've read, I get the impression that many of Rand's single female groupies viewed Rand as a kind of romance novelist they wanted to hang with. Their presence at NBI events provided an incentive for Rand's single, mostly geeky fanboys to show up and play along with Rand's delusions of grandeur. Despite NBI's relative obscurity, it did attract many thousands of participants and students before Rand had her fight with Nathaniel Branden and he shut down his part of the cult.
By contrast, something about cryonics just doesn't appeal to women in significant numbers, which therefore makes it unsuccessful as a "cult." I suspect cryonics' pro-male bias accounts in part for its failure to cross some threshold into a thriving state.