Yes, predicting the stock market does involve predicting what other market participants (and hedge fund bros) are going to do.

But, to predict what other market participants (and hedge fund bros) are going to do, you need to predict any world dynamic that will have an eventual effect on stock pricing.

The most successful quantitative funds (RenTech, 2sigma etc) consistently make billions of dollars in cash each year because they have collected the data sets that allow them to do this better than others. But they are still a long long long way off from having a true world model.