Waifu monetization model, more profitable to milk a lot of horny folks a little for a long time. I still can't get over Mihoyo built a tokamak reactor IRL.
Please do not milk the horny folk. ;) Well, they invested in one, and they also invested in a SpaceX competitor, Orienspace, too. It was a little jarring seeing their logo alongside all the ~serious companies.
Not just monetization, these types of games also pivot towards building parasocial relationships with in-game characters to you. This leads to people building zero tolerance for what can be perceived as other characters interacting to them - an issue that affected Girls Frontline 2.
International Genshin players, however, do seem to embrace "shipping" (pairing two in-universe characters in relationships) instead, but these also have their own internal controversies - look up "shipping wars".