Can you blame any writer for fleeing that sinking ship?
I can, and do, when I personally contribute many of the things I hate about Marvel today to his juvenile writing style and poor characterization. That being said, you are right, he probably realized it was time to jump ship.
I hope DC makes him earn his way to a high profile book. I really couldn't stand the idea of the Justice League sitting around a table for 7 to 8 pages telling lame jokes and talking about their various hook ups.