There are a couple factors with that. Firstly, he's not a voice actor. He's talented, but in other areas of acting. Secondly, they mentioned that he's not anywhere near as available as they needed him to be to get the lines done properly. So they needed to go with someone more open. And let's be honest, his voice acting was mediocre at best. I love him as an actor, but even the best of the best can -blam!- up sometimes.