Of course they can not predict the future in the strong sense, but they may be able to extract some fraction of a bit of information about the distribution of p

Of course they can not predict the future in the strong sense, but they may be able to extract some fraction of a bit of information about the distribution of possible outcomes, slightly reducing the variance. This is enough for a hedge fund to make money. Similar to knowing something like how full a department stores parking spots have been over the last quarter. It won't give you an accurate prediction, but it can give you a slight edge over the competition.