115's? Really? And yes, a couple girls moved up. But you compare the talent levels or the rosters at the various weights. Even before she pissed hot, Cyborg was talking about moving down because there was no competition at 135.
And yes, Carano had much greater marketability than Cyborg. Hell, she still does. And, of course, Carano had the same issue as Cyborg: fighting smaller competition constantly. Girls routinely moved up to fight her as well. Of course she only fought 7 times before running into Cyborg. Anybody picking Carano to win that fight beforehand was thinking with their dick.