A game can be massively popular but many many games fail to hit the mark. Many do not see success and many do not even ship.

Ok, but Fortnite is a massively popular success, even as its popularity slips. Fortnite's run so far could have sustained Epic for years, even without other revenue they get from things like Unreal Engine. Games as a whole may be a risky venture, but we're talking about Epic here; the mystery is not how to succeed in games, but how a company that had an earth-shattering run of success in games is now in such a position.