The Fables writer has said that he struggled with working in the shared superheroes' world, where he had to coordinate his writing with other creators and titles.
"I need to learn that when I do things in the DCU that one should not plan too far in advance because you're going to get your heart broken because plans change on the fly, a lot," he told Newsarama.
"With JSA... I finally got all the characters into the right position to really start doing what my long-range plans were. But one of those plans was that this was not going to be a grim and gritty group of anti-heroes.
"I'm tired of the 'fill-in-the-blank turns evil and everyone's got to fight the evil version of this character'. It even fit within some of the issues I did, that 'we're not that type of person anymore'.
"And then comes along this crossover in which the whole plot revolves around just about every member of the JSA turning evil for a couple of issues."
Willingham's 12-issue run on JSA ended last year.