Okay but it does also have something to do with Earth One being a success and DC wanting a second one out sooner. Having him leave both titles to do a second volume ensures that this will come out sooner than it would have had he just been working on it on the side. They obviously want another one out quick as possible.
I hope a second volume fares better than the first, but if they're rushing it out I probably won't even bother. Easily the worst take on Superman's origin that I've read. I liked some of the concepts he introduces, but otherwise it was just plain poorly written. Artwork was decent, though.