1. The Medallion Fund went insider-only 17+ years ago. The best explanation for their performance - assuming it's legitimate, since the fund itself isn't audited - is that they use an extreme amount of leverage to multiply "safe" returns. Of course, it's much more likely that the information being leaked to WSJ is a marketing ploy to keep investors in Renaissance's two publicly available funds, both of which greatly underperform the S&P 500

2. BRK is dead even with the S&P 500 over the last decade. This is despite the fact that BRK has access to cheap/nearly free leverage

There are better examples out there if you want to critique EMH.

The original point still stands. The vast, vast majority of professional investors (let alone retail investors) underperform the market. Almost everyone who promises safe alpha is full of it.