This "Superman UE5" is only 3 Unreal Engine assets from the marketplace.
- City Sample by Epic Games.
- Superhero Flight Animations by Indie-us Games
- Superhero Constructor by BL
It's a 5 minute mesh swap and drop the character in the level amount of work that even my grandmother can do with minimal UE4/5 knowledge. He's not stealing this guy's work because there is no "work" to be stolen. Don't assume things you don't know.
In fact, SHEOL from the video you linked seems to have done even more work on their project because there's a FPP camera mode and a sonic boom midflight and the locomotion animations are from Hammerhead whose Flight Animations are arguably better than Indie-us' IMO... and in a later video, heat vision and vehicle destruction.