they drew pa-13 in hopes of stealing it. they had no shot at all at landing it and should have realized this. they should have stuffed all the dem votes they could into that district.
But PA-13 always was pretty full of Democrats. Their plan, which I'm sure you're familiar with, was to have a Philly Democrat win the primary and lose to a MontCo Republican. But that part of MontCo and NE Philly have become so reliably Democrat in federal elections that the plan never had a chance. There's no pool of Republican voters there that could have helped out elsewhere. If they'd given more precincts in Philly to PA-08, those precincts would have supported Patrick Murphy, as Fitzpatrick's strongest card was his service as Bucks County commissioner. The parts of MontCo and Philly already in his district were as Republican as they get.
Pennsylvania has seen the biggest change in voting habits since redistricting of any state I can think of, bar New Hampshire, where it doesn't really matter. Georgia is the only other state that compares, with huge numbers of Gore-voting rural white voters shifting to Republicans. They did the best they could with the maps but you can't hold against a paradigm shift. Remember, PA-06 was supposed to be a solid Republican district when drawn and it was considered the most likely to fall this year. Only Gerlach's campaign skills saved it.