I don't think it's a brain thing with him, it's a physical tools thing. His arm and footspeed are both 5th percentile. That's not a great place to start building a 2b from.
He started out well, but I suspect it became clear internallly as he went along that the more time he spends there, it was only going to go one direction defensively.
I think there was a point where was +4 OAA and then plummeted to +1 over the course of a week. Yes, small sample overall on his defense at 2b, so variability could be high one way or the other, I think they decided to pull the plug while they were ahead, knowing they can stick him there in a pinch.