I agree with the other person that the JC fan club-cum-cult only became a real cult heading to religion after it had the sacrificial death to lean on.

The escape velocity was achieved not from the leader dying, as the martyrdom was the key factor long-term, but more so that it survived the core group of founders by being pliable. It wasn't the "message" per se, but the decentralized and un-professionalizing of the religion that made it so that anyone could practice it, and for less hassle and cost than existing religions. It reached escape velocity because the barrier to entry for outsiders to practice and become leaders was lower.