Given that a potentially-psychedelic brew was ingested at the climax of a mystery cult, and it is written that he"is found to have taken part in all the traditional festivals and sacrifices. […] he says that he shared in all the festivals […] and that while he was joining in celebrating the festival of the Choes [at Anthesteria] and the urban mysteries [Attic Dionysia] | and the other festivals at a meagre dinner..." it would might been odd for him not to ingest kykeon.
If something like kykeon was ingested regularly, and kykeon can contain ergot, or potentially another psychoactive agent, then ... well, indeed, "knowledge of the gods" was "evident".
I agree. As per Wikipedia, it seems quite certain that Kykeon contained ergot, which might make Epicurus' idea of the gods and the intermundia much more conceptual-spiritual (for lack of a better word) than physical – which does not make them any less real, because we can sense them…?
For those wondering: Ergot is a fungus growing on cereal grains, which produces a wide range of bio-active chemicals such as ergometrine (used as a drug after childbirth, still an essential in many parts of the world), but most notably for our discussion here would be ergine, which is LSD minus the diethyl group, which in turn is like magic mushrooms' psilocybin plus a mild amphetamine, which I'd guess to be very vaguely comparable to being stoned-out-of-one's-mind on cannabis while also having ingested enough caffeine to offset the tiredness/numbness/lethargy/… that would induce. (Oh my, the weird knowledge my sponge-and-sieve brain decides to remember! *shrug*)