> At the time I guessed that he was much smarter than me — that it would take me years to become as investment-savvy as this guy was.

You lucked out by mistakingly believing he was intelligent. The classic scenario is when your neighbor is obviously an idiot, making tremendous amounts of money in the market, and you have to explain to your spouse why you can't/won't emulate them. That's when even bright, (normally) level-headed people start piling in before the bubble bursts.