Part of the "certain level of expertise to talk yourself into something extremely dumb" is because we've all heard the stories of genius ideas that were dismiss

Part of the "certain level of expertise to talk yourself into something extremely dumb" is because we've all heard the stories of genius ideas that were dismissed as crazy. And if someone considers themselves "smart", then they think they can identify those opportunities before the general population. This leads to both/either FOMO ("I don't want to be considered dumb because I didn't invest in X") or self-optimism/egotistical ("I'm smart because I found the Next Big Thing"). These two factors explain a lot of the cases where supposedly smart people talk themselves into stupid decisions. Or as another commenter posted, these people are not really "smart" or are smart but not "wise", because a wise person would recognize such situations and be on the other side of the stupidity mountain into enlightenment land.