from what i can tell the story hooks people enough to play and the designs are appealing enough to reach a broad audience. genshin also is open world so it appeals to people who enjoy open world mechanics. (that was my main reason not to play because i don't enjoy open world games)
i think it also helps that it is cross-platform, even if the engine isn't optimized for genshin. it makes it easier to get people into it.
Re: genshin/honkai/wtfever
i think it also helps that it is cross-platform, even if the engine isn't optimized for genshin. it makes it easier to get people into it.