There would be no Fortnite if it wasn't for Brendan Greene aka PlayerUnknown, who is basically single-handedly responsible for creating the Battle Royale game genre. I see no problem in him attempting to make some money on his creation before a AAA giant comes in and sucks the air out of the room.
It's been a point of contention recently, the question of who created battle royale. Perhaps Greene is responsible for the modern iteration of it, but the last-man-standing concept has been around in gaming since Bomberman in 1983. And the concept of battle royale in general was popularized with the Hunger Games and of course the film named Battle Royale. And, "battle royale" as a phrase was used by Ralph Ellison in 1952 in his classic novel Invisible Man, describing a free-for-all boxing match that the protagonist must participate in. So Brendan Greene didn't come up with this out of thin air, or at least he wasn't the first.
On the other hand, I see no problem with him trying to profit from it either.
Edit: I correct myself -- in Invisible Man, the phrase was "battle royal," not "battle royale." It's still clearly similar however.
Bomberman shrank the arena when the matches went to sudden death. Pretty sure others also did this (certainly common in single player games of that era and earlier - arguably Joust with it's rising lava is close to being the first for that sort of thing)
While Battlegrounds was not the first battle royale game, its release to early access in March 2017 drew a great deal of attention, selling over twenty million units by the end of the year,[18][19] and is considered the defining game of the genre.
That's what the grandparent was saying: Brandon Greene, the man mostly responsible for PUBG was also responsible for H1Z1 (SOE licensed the Battle Royale mode from him for H1Z1 and hired him as a consultant):
https://www.pcgamer.com/battle-royale-modder-brendan-greene-...
That's a mighty large statement. He may have made one of the most popular games but he certainly did not come up with the idea in gaming (Minecraft mods based on movies) or in movies (Battle Royale is a Japanese movie from 2000).