Oh, they believed him. They just have no clue about unintended circumstances. He promised them free stuff - they couldn't see the ramifications.
I agree that some believed him and supported his agenda. Some of my friends, though, refused to believe that what obama said was what he meant. They just thought he sounded good and seemed nice. I think it was a matter of “anybody but Bush.” But, yes, I think you’re right, that they didn’t understand the consequences. That seems to be a hard concept for liberals to grasp - there are consequences for actions.