Idiocracy (The personal traits exhibited by an individual; e.g., "idiosyncrasy"), being the opposite of Conformity (Appearance or actions in accord with prevailing social standards, attitudes, and practices), then I'd say that idiocracy is not inevitable.
However, if the definition is extended to encompass the idea of a government run by idiots, or with preference give to idiots in matters of hiring, housing, and jurisprudence, then I'd have to say that idiocracy has already happened, and we are only now beginning to realize it.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.