The rigging had little to nothing to do with how both groups turned out.
At the time with Produce 48, Produce still had strong brand power and a built in fanbase. Whatever lineup they result in, the group would've done the same even if they swap out Jo Yuri and Kim Chaewon with Chowon and Gaeun (the two most rumoured rigged in contestants). And with a concept and debut song already decided. People like to claim Chaewon and Yuri fit in the concept and how Chowon and Gaeun would not have, that's all bs and self-rationalisation. Like everyone else has said, this is the lineup people are familiar with and the only one you know. If Lee Chaeyeon didn't make the lineup, you all would've said she wouldn't have fit the concept because of her visuals. But as long as the lineup has the core members like Jang Wonyoung, Sakura or Minju, any other members would be fine in the background because those members are the face of the groups and represent the group's identity.
Rigging the lineup wouldn't have helped Kepler in any way, they had a rocky start with the show itself with all the different rules, trying to differentiate itself from the original Produce. There was a survival show fatigue with this essentially being season 5 of Produce 101, and the general public has completely turned away due to the rigging itself. Their sounds and concepts are hardly public friendly and any kind of member change done with rigging wouldn't help at all. Who can you put in this lineup from GP999 that would've helped the group? The other popular trainee was Yurina, but if even Xiaoting can get buried in this group, how far can another foreign member realistically take them?