Sin is loads of fun. If it wasn't, then it wouldn't really be tempting. It's fun to sin, that is until you start to realize the consequences. Selfishness (and that's what sin really is) has its momentary reward, but the consequences will hurt you, then the guilt will finish you off.
I think people started to realize that they had screwed up when the sky went dark at noon for 3 hours. It's kind of one of those "Oh crap! What have I done!" moments. I hate those. JM