Ah yeah, remember when Epic Games stole the concept of a popular multiplayer battle royale game? I'm talking, of course, about The Culling, a game about a year older than PUBG. And other than the 100 player sized games and parachute mechanic, it's frankly not that different from the rest of them.

Snark aside, PUBG built a little on the battle royale formula. Fortnite built a little on the battle royale formula. Both Bluehole and Epic Games were madly successful. Maybe PUBG would've done even better had Fortnite BR not done so well as a free to play experience. But it could've also done better if it wasn't a buggy mess for like an entire year after launch, one that costs $20 and never seems to be on sale.

There's a reason gameplay mechanics aren't copyrightable. This is how game design evolves. I'd hate to live in the world where ID software permanently owned the rights for making first person shooting games.

One could certainly argue there is some conflict of interest in that Epic Games has a conflict of interest because they licensed their engine to Bluehole. But Unreal Engine is a fairly popular game engine, and I think it's unreasonable for them to not be able to be inspired by games written on their game engine.