I think it's a combination of things. On the one hand, the phone records issue is the most easily understood by the general public, and so it already had traction there. It sort of fell into the government's lap that they could focus all of their press' attention on that issue in particular.

I agree doubly so however - the phone records are near the very bottom of the list when it comes to the severity of what Snowden's(and possibly other's) revelations have brought to light.