It is not just his knowledge of the playbook but his arm strength as well (something that I think a lot of people take for granted and don't realize how strong his arm is). All of those back shoulder passes down the sideline, the 15 yard out patterns, and the ability to get velocity on his ball from "poor" throwing positions makes a huge difference.
Those 2 pass pattern I mention above do not happen just because he knows the playbook or is in sync with his receivers, they happen because of his arm strength combined with the other stuff, there are maybe 5 QB's in the NFL that can effectively throw those routes. I think most experts would put Rodgers, Flacco, Stafford, Cutler and Brees in the top 5 for pure arm strength and the only guy that can match Rodgers accuracy is Brees.