I know that it has been a few days, but I was thinking of other possible divergences. Batman went through at least two distinct crisis of popularity. One was in the period after the Adam West show ended. He was retooled as a character and successfully saved. The Dark Knight Returns was the end result of a two decade effort in the comics to divorce him from the show's dated camp. So you could abort that effort by having Denny O'Neil stay away from him for whatever reason and have D.C. decide rescuing Batman from identification with West's show is a lost cause. The other moment of cultural unpopularity was after Batman and Robin. As happened in the 1970's there was a great effort to divorce him from camp. So another divergence could be keeping plans for a new Batman film trapped in development hell after 1997, no Batman Begins, and have another franchise take Nolan Batman's cultural space. Of course killing Batman Begins could have a more wide ranging impact. I don't have the background to say precisely how this is the case, but I see the fingerprints of that movie on almost all the Superhero franchises that followed it. Arguably, it was Batman Begins, not it's more successful sequel, that had the most influence on the genre. If I'm right preventing it may have considerable effect on Superhero films generally.