Presumably the parent meant that Bogle popularized index mutual fund investing in 1976, thereby catalysing the passive investing industry. And whereby there we

Presumably the parent meant that Bogle popularized index mutual fund investing in 1976, thereby catalysing the passive investing industry. And whereby there were previously only actively managed funds, the creation of that industry substantially lowered the cut money managers got from person wealth management. Thereby leading to generations of people with more control over their money and willing to take risks, where a professional money manager would have little incentive to invest in startups with wealth locked up in their funds.