> I can't understand why otherwise intelligent people
Intelligence isn't prophylactic against conspiracy theories, and crypto-cultism has all of the major features. It offers an alternative worldview where global elites are engaged in a massive conspiracy to keep the little people down, but with one weird trick the enlightened can stick it to the Man. Take fintech out of it and you're looking at a cyberpunk novel.
Crypto cults are technology based, so it strokes the ego of cultists already in technology fields: they're superior because of their existing skills and expertise.
Finally, crypto trading has indeed made some people quite rich, and they're happy to evangelize. Doing so works for Amway and other "don't call it a pyramid" schemes, and the mass delusion of cryptocurrency doesn't even have a living board of directors to point to as the ultimate extractors of value.