New ideas need concealment for protection while still weak [causal]
Under these conditions, the secret society is the suitable social form for contents which still (as it were) are in their infancy, subject to the vulnerability of early developmental stages. A new insight, a young religion, morality, or party, is often still weak and needs protection, and for this reason conceals itself.
XREF: Echoes sociological work on deviance, secrecy, and the sociology of knowledge—e.g., Simmel's own work on secrecy, and notions of subcultural incubation.
Georg Simmel, The Sociology of Georg Simm…, loc. 8369