The same thing happened to Guillermo del Toro’s Justice League Dark movie (now it is in the hands of J.J. Abrams and Bad Robot).
It almost makes one wonder how many times a dark DC Comics property was softened by studio interference to underwhelming results.
I can think of one, or maybe two.
The Sandman, which actually is getting a Netflix series, never became a movie due to reported creative differences over it development, most likely because the Neil Gaiman and Joseph Gordon-Levitt, who was attached to direct and star at one time, wanted to go darker than New Line Cinema was willing to go with it.