I remember that hitting home for me when I saw a "stable coin" that was mechanically equivalent the a sort of economic perpetual motion machine raised over $100M from reputable investors. Not just a $100M+ valuation, a $100M+ raise. Nobody I talked to who had actually read and understood the white paper was surprised when they folded after not launching, blaming regulators rather than taking ownership of the fact that it was a flawed premise.
They apparently returned 90% of it, I'm not sure where the $13M was spent. (To be clear, I'm not suggesting this is a scam per your definition, just a failure of DD on the VC's part.)