Well, you have to keep in mind that back in early 2008, Ryan had already been enshrined in the HOF. Kind of the way Luck is already in the HOF.
To be honest, yes, we can say that would have been idiotic of us, but on the other hand, I thought Ryan was going to be a bust (and Flacco the best QB in the class -- yes, I thought these things BEFORE the draft). Point is, it's all opinion. If you feel that strongly about a guy, especially one who was as "pro ready" as Ryan was and we were in win now mode, you do what it takes to get him...within reason.