That is hard to prove, and is also not necessarily useful for anyone making a choice of where to invest, if the rare events are pretty unpredictable and "pretty

That is hard to prove, and is also not necessarily useful for anyone making a choice of where to invest, if the rare events are pretty unpredictable and "pretty hard to pull off" they may as well be treated as random by investors. There clearly are strategies that make money at times. The majority off hedge funds do not offer these, and what they offer is hidden by their fees, which do not correspond to results, and even discourage good results as they encourage volatility.