So to compile what people have said:
1. poopy advertising: plain yellow sticker at the very top of the bubble (if anything, remove those useless "Secret" Code stickers and put the Bric stickers there.
2. two concurrent mail-aways at the same time: rocket-firing toys, I'm pretty sure, attract kids more over some unheard-of big-headed dude with no play features.
I also think it has to do with character choice. Keep in mind Nahdar Vebb was a top-wanted character, and Hasbro had always said 'no' to us. But then give us Bric, especially when we have no clue who he is. Even when Rex was a mail-away, there was demand because the new movie and entire series was coming out, and he's also one of the main characters.