Again, Sanders is not a newbie, and his previous film cost $60 million more to make than this did. He undoubtedly got the job as a result of Snow White and the Huntsman winding up as a minor success and could be seen as a pretty safe choice to go with that would also not be particularly expensive, compared to a more established director.
He only did one feature film prior to GiTS, effectively making him a newbie at directing feature films. Before Snow White and the Huntsman, he couldn't even be classified as a newbie in that department. Until he has a at least a couple of films under his belt, he will be regarded as a newcomer.
No studio in their right mind should give newbies a chance to direct blockbusters. You don't let a pilot that has never flown a plane before start flying jumbo jets frequently. They need to build up their skills, and they do that by acquiring experience. That goes for any profession or goal for that matter. Start small, aim big.