>>527346816
steam commissions a cut of profits from the games that it carries, something in the vicinity of 30%. iOS does the same thing but to virtually any company it's worth it to access the easily exploited and deep pocketed Iphone market.
Presumably Epic Game Store gave Hoyo an exceptional deal, as they often do, and are taking either no commission or a negligible one. In fact, EGS might be paying Hoyo to carry it. They have a habit of throwing money at relevance sometimes.