Abstract: Why did the Beatles become a worldwide sensation? Why do some cultural products succeed and others fail? Why are some musicians, poets, and novels,, unsuccessful or unknown in their lifetimes, iconic figures decades or generation after their deaths? Why are success and failure so unpredictable? On one view, the simplest and most general explanation is best, and it points to quality, appropriately measured: success is a result of quality, and the Beatles succeeded because of the sheer quality of their music. On another view, social influences are critical: timely enthusiasm or timely indifference can make the difference for all, including the Beatles, leading extraordinary books, movies, and songs to fail even if they are indistinguishable in quality from those that succeed. Informational cascades are often necessary for spectacular success; in some cases, they are both necessary and sufficient. For those who emphasize social influences and informational cascades, success and failure are not inevitable; they depend on seemingly small or serendipitous factors. History is only run once, so this proposition is difficult to prove. There is no question that the success of the Beatles, and the rise of Beatlemania, involved an informational cascade. But whether and in what sense that success was a product of serendipity, or contingent on factors that are elusive and perhaps even lost to history, is essentially unanswerable. If ‘Love Me Do’ had not been a hit, it is not entirely unfair to wonder whether the Beatles would have enjoyed anything like the spectacular success they had. We may doubt that in a counterfactual world, there might have been Kinksmania or Holliesmania, but research on ‘Lost Einsteins’ suggests that it might be reckless to rule out the possibility that some other band, obscure or unknown, might have taken the place of the Beatles.