Ben Affleck has revealed in an interview with The New York Times why he decided to depart the Batman movie. In short, it was the Justice League movie and the troubled production that took place.
Ben Affleck expressed in an interview with New York Times, that the previous Batman role he had taken led to dark times in his life where he struggled with alcohol abuse and subsequently had to check himself into rehab.
Ben added that it was his expereince as a whole on the DC ensemble flick that ultimately pushed him away from continuing the role as Batman and also writing/directing his own solo movie project. This was only worsened due to the poorly received follow-up Justice League which was subject to mutiple rewrites, reshoots as well as a director take over that saw Zack Snyder depart from the role and Joss Whedon take over.
With Ben moving on from the Superhero scene, Matt Reeves has taken over the director role of The Batman and has brought some interesting and fresh faces to the DC camp, including Robert Pattinson, Zoe Kravitz, Jeffrey Wright and many others.
It was just last week that Matt Reeves revealed the Robert Pattinson Batman costume. You can check out the cool design here.