The source selection rationale is apparently out for the CEV decision:

Doug Cooke, NASA’s source selection authority, wrote in the Aug. 31 document that although both team’s proposals were sound, Lockheed’s possessed a “clear advantage.” Both received ratings of “very good” in overall mission suitability, but Lockheed’s was numerically ranked somewhat higher because of its superior technical approach.

…Cooke deemed Lockheed’s past performance on Phase 1 of the CEV program “exceptional,” saying there is “no better predictor” for how a company will perform in Phase 2. Lockheed’s past performance was rated “very good,” and Northrop/Boeing’s was rated “good.”

Good apparently wasn’t good enough.

I wonder if Northrop Grumman and Boeing are reconsidering their future relationship. I think that part of the strategy of the team became obsolete when Admiral Steidle was forced out by Mike Griffin. It looked as though the team was designed to appeal to him (having Northrop Grumman, a major Joint Strike Fighter contractor) leading would give him more comfort than Boeing (Steidle was in charge of the program during its development). But with Steidle’s departure, the spiral development concept vanished, as did the NGB basic strategy.

I suspect that there was a lot of complacency on the team as well, though, due to all of the manned space heritage within Boeing. Many probably couldn’t imagine NASA going with anyone else.