>>667895Because Nijisanji never had such separation between male and females that HoloProductions have.
They always could interact and benefit from every member in collabs and all. Yashiro and Kuzuha play family with Himawari and Dola; Ririmu, Kuzuha and Shiina also form a unit; Banderas and Roa were like father and daughter toiling on late night minecraft; and Utaku was thisrting over Masaru's shota dick; a lot of Kanda's popularity comes from teasing Mirei extensively and all the sexual tension that comes from it with Shiina and Hoshikawa actively shipping the two; Kuzuha interaction with Mito gave us the weather deck meme, etc. EX-Albio's popularity was greatly boosted from his teacher-student interaction with Ars - those are just some of them and that's not counting interactions with people from other companies and indies.
All those memorable and meme-worthy moments helped to boost their popularity.
They also are not pigeonholed on being cool idols, Yashiro, Maimoto and Rikiichi for example are extremely awkward otaku and for a big part of the audience that fell right into the "oh man, they're just like me" category and fulfill the role of being online bros to the audience - which let them eventually display their other talents.
Meanwhile, the only one who's doing anything comparable this in Holostars is Roberu, who became his audience surrogate son and get his funny meme-worthy moments out of his interacting with people outside of outside of HoloPro.