I recall that talking to overly ostentatious people in nightclubs as to what they are doing for work was a canary in the coalmine for lots of large scale fraud, especially when it was apparent in any discussion with them that they were far from the intellectual capacity to understand what they were doing.

2000: "I'm daytrading in dotcom stocks"

2005: "I'm a mortgage broker, want an interest-only mortgage?"

2020: "Crypto baby!"