I'm genuinely interested in how this company is bleeding money when their engine powers two of the biggest games in the world right now, Fortnite and Genshin Impact
Ignoring the wrong game, Unity doesn't make more money when a game made in it sells more. Unreal gets a percentage of game royalties, Unity does not. Unity charges an annual fee to use it in development. So a game made in Unity could earn $1 billion/year, Unity would only get $1800/year for each development seat. And if that $billion game was made by an indie, they wouldn't have needed to pay a dime to Unity until the following year, as Unity charges based on how big your company already is.
Unity *does* get a percentage of ad revenue, if you use their ad system. But there's nothing forcing you to use Unity's ad system except convenience. As I understand it this is Unity's main revenue stream.
If a game made in Unity becomes wildly successful, such as Hearthstone, Cuphead, Cities Skylines, Ori, all Unity really gets is good publicity to attract more developers.