It’s become standard for the show to have one solidly conservative co-host (which, despite plenty of rumors, still looks like it will be Meghan McCain when the new season starts), but the producers may want to have someone who is at least more understanding of the conservative viewpoint, to help discussions along, in the hopes that conversations don’t become as contentious as they’ve sometimes been in the past.
Audiences are already familiar enough with Sara Haines to jump right in and accept her when Season 24 premieres, but her being more middle-of-the-road may have helped along the decision to try and bring Haines back in.