Republicans held the predecessor seat, because Democrats lost a usually safe seat in 2010 due to a corruption scandal. The gerrymander attempted to shore up the incumbent, whilst still leaving him enough of his base to win a primary.
Good point.
It's important for us to remember that partisan gerrymandering isn't strictly about partisan gain. Incumbent protection/primary defence also plays a role and can conflict with maximizing one's seat count.
At the risk of being a giant jerk, this goes to the heart of a disagreement I've had with certain other posters on here--parties don't just draw maps to maximize their power, but also to make things easier for incumbents and satisfy parochial concerns.