There is a lot of reasons for Holostars to exist. Hololive lost viewers to Nijisanji, particularly due to the lack of male vtubers, and the fucking segregation - segregation that like it or not, will end fully end eventually. Cover made it clear many times, that it doesn't like traditional idol culture, and they want to break that tradition. The idol concept of Holo is just aesthetic. Cover plans to grow and expand holo, and it time break the walls. Even if the unicorns get angry and leave, they will get replaced by more casual fans. At the end of the day, unicorns are bad for business, as they are stressful for talents to deal with, and can turn against their oshi's for the dumbest of reasons. There is a lot of bitching about Niji sisters here and how disloyal they are, as if the males hadn't been canceling vtuber girls for years, for all sort petty reasons. Ironically, the first waves of EN fans of Holo, where very chill. When the JP audience tried to eat Towa alive because they heard a male voice in her room, it was the Western audience who had their back. Back then, the idea of caring about the personal lives of vtubers was ridiculous, and not wanting them to interact with males, it was something only mentally ill JP otaku cared about. It was this fucking community that brought that cancer to Hololive.
POTENTIAL AND THE FEMALE MARKET
So back to Holostars - there is a massive female audience to tap in. This was obvious in Japan with Nijisanji, which is dominated by male vtubers, with a dominant female audience. But is also Nijisani that showed Cover that there is a massive audience for male vtubers in the West too. There is also a substantial male audience, who would rather watch a male vtuber than a female one. Those are all niches that Cover would be insane to not cover. Growth potential will always be there. What Stars always needed was that one Coco-level talent, that would break walls and bring attention to it. Moreover, especially StarsEN had been held back by a hate campaign, that didn't necessary came from Hololive. Lot's of Vox sista's have been rather scared of StarsEN since the start. But in any case, even if is slow now, Stars is a bet that will eventually deliver... Plus, the reality is that Stars look like a flop only because peoples compare them with Hololive, but, in reality, they are above most corpo's, and for most part, they get similar and better numbers than NijiEN.
PROFITABILITY
Additionally, they are more profitable than you think. Betle from StarsEN for example, is somewhere in the middle when it comes to earnings, exceeding even many JP Hololive talents, Towa, Kanata, Nene, Fubuki, Ayame - he made nearly double what Suisei made in SC's - HoloEN like Mumei, Bae, Korni, and even other big names outside Holo, like Kson or Salome, Patra, Kanae and Luca. Is dumb to just look at CCV's and conclude how popular someone is, because a 500 CCV of loyal whales, is more valuable than 30 000 viewers that don't spend on you. Gura for example, has never been a leading figure in Myth when it comes to SC's. Scarle Yonaguni from NijiEN on the other hand, is the biggest female NijiEN SC earner, despise a low CCV.