My guess is the Falcons knew of RG3's strengths (deep throws, etc), so they gameplan to take that away. Therefore Kyle calls more runs and shorter passes. Then when Cousins came in, the defense started stacking the box, making Cousins throw it to beat them. He did just that, so they drop back again. You'll notice that Morris couldn't run until that throw to Moss was completed, then when they dropped back he immediately broke another long one?