Why was he allowed to transfer in the first place??

According to what I've read about Bush's National Guard service, after accepting a position on a campaign in Alabama, he was transferred to the Alababma National Guard. When he got there, they didn't have the plane he knew how to fly, so he ended up sitting on his ass for six months. And that's Bush's version of events.

So here's a question I haven't seen asked anywhere : Why did the National Guard let him transfer if they knew he wasn't gonna do a damn thing? Is it normal for the armed forces to transfer people to places where they're useless in the middle of a war?