It was in the early 1990s, after three or four years as a correspondent at CNBC, that it became obvious to me: The vast majority of active managers rarely beat their benchmarks.

Sure, there was Bill Miller (Legg Mason Value) and Peter Lynch (Fidelity Magellan Fund), but they were distinguished by their rarity. They were famous precisely because it was so rare for anyone to outperform for more than a few years.

That was when I became a Jack Bogle disciple.

It was not just that active managers didn't outperform. A large part of the problem was the high expenses. Even into the early 1990s, it was not unusual for mutual funds to charge 1.5 percent per year, or even more, for "active management."

Bogle's central insight was that money managers were almost never worth their high fees. In 1975, he created the first index fund built around the , initially operating under the name First Index Investment Trust.

It attracted $11 million in that first year.

Bogle, who died Wednesday at age 89, outlined the reasons for the creation of the trust in a 1997 paper: "The facts are: (a) most professional managers fail to outpace appropriate market indexes, and (b) those who do so rarely repeat in the future their success in the past."

Indexing was not his only insight. He sought to outperform by keeping costs as low as possible. He said, "You want to be average and then win by virtue of your costs."