I saw a Reddit comment that said that a major reason for Bayley losing her momentum was because she got injured. She was gone for about a year or so and during that time, they were performing in front of fans again. Everyone who started gaining success in the Thunderdome (Roman, Jey) were able to capitalize off that and keep their success. By the time she came back, WWE was already putting their resources into other women and she didn't have the same spark as before. Her winning the Rumble, turning face, and feuding with Iyo should have been a bigger deal, but it got drowned out by the Rock situation and as far as the women went, Rhea/Becky was treated as the money match.
Another comment I saw said that beating Bayley doesn't mean anything because she puts everyone over. Charlotte doesn't lose often, so Rhea and Tiffany benefited a lot from beating her. Bianca officially became a top star when she beat Becky at WrestleMania, and Liv bragged about being the last person to beat Becky before she came back. When Bayley loses, nobody elevates from it. I think Roxanne could have benefited a lot from working with her, but the fact that they dropped the feud means they don't even think it's worth doing. They would have never done that to Charlotte, and it's clear that Becky is only there to work with Lyra, so they can't do that to her either.