Maybe I'm not remembering, or ill-informed, but the only animes that aired in the conventional, Saturday-morning slots that had success were stuff like Pokemon, Yugioh, Digimon, maybe Beyblade. Basically franchises tied to aggressive merchandising. Along with 4Kids bad production, it's probably why One Piece didn't take off for that demographic, despite being initially aimed there. It's all about toys and games in addition to the show for that demo. Even Naruto, which wasn't aimed at the Adult Swim audience, initially, didn't air until later in the day. Keep in mind that the Toonami block of anime, which made DBZ popular years ago, was gone by this point, IIRC. The majority of anime, regardless of it's intended audience in Japan, airs at these late-night timeslots. Unless you are on a system that has Funimation's channel.