Dividend yields averaged about 5% during that twenty-year period, helping boost the annual return to 8% (after inflation) for people going "all in" at the bottom in 1932. A significant difference between then and now: dividend yields were over 10% in 1932, today they are 2%.
An excellent point. Risk awareness has increased recently, but the pendulum will swing the other way when institutional memories inevitably fade, allowing the cycle to continue.