I can't make the claim that "the author started a death cult", but I will say that they and their followers are closely patterned from the self-help grift template of endless seminars, and their ideology centres on moral absolutes and arguments that are intended to be so compelling that they describe some of their ideas as an "infohazard".

Using only pop culture and fiction as primary sources, the "rationalism" subculture intended to create a system of ideas that was undeniable, according to its own logic - and then they accidentally spawned subcultures due to differences that were irreconcilable because of (I feel) their own absolutism. And if you follow these things, a subculture within a subculture is, 7 or of 10 times, a cult.