The argument isn't that passive index investing is some kind of perfectly optimal investing strategy, it's that it's the most practical strategy for 98% of normal small, individual investors. If you don't have millions of dollars to invest, and you have a real job that prevents you from spending all your time researching investment opportunities, then you are probably better off just buying the market, instead of flailing around paying fees and trade commissions trying to beat the market.
If you believe in the weak form of the Efficient Market Hypothesis, and you are not a professional investor, then you should probably be in index funds.
You're almost always better off with an index than the "HR Director Got a Kickback Growth Fund"
Bogle started the First Index Investment Trust on December 31, 1975. Bogle founded The Vanguard Group in 1974; it is now the largest mutual fund company in the United States as of 2009.
[ source : https://en.wikipedia.org/wiki/Index_fund#Origins ]
I would like to know how.
I'm not suggesting "anybody can do it" but the study that concludes money managers underperform the market often gets stretched into "nothing beats index funds".
Anecdotally, I spend about 3 hours a week on financial research. I've averaged 13% returns since investing in high school during the 90s.
Nothing wrong with index funds, but the boglehead position isn't axiomatic.
The very act of noticing that something is a good strategy, and beginning to trade on it, will over time drain away the utility of the strategy, until it is useless or worse than useless.
Tracking indexes is "big", and has some brute simplicity about it, but eventually the market will eliminate that as a viable investment mechanism. (But that won't stop your metaphorical Dad from swearing up and down you need to buy index funds....)