I'm guessing that's exactly what burry is doing. Let's assume that he is right, and the S&P 500 index is over valued. A big reason why it keeps staying that way is because for the past 10-20 years, there has been a lot of marketing selling these index funds. At this point, most people agree that investment for retirement generally involves putting money in an index fund and that's what people are doing. A percentage of their paycheck goes here.

So, for burry to win, he needs to inform the world of the situation. And when enough people act by stopping contributions to index funds and/or sell their positions, burry is gonna make a killing.