Funny how people tend to think things in reverse of the actual truth. This manga is the adaptation of the 1999 novel and was released in the same year (2000) as the movie which is also an international success (especially for a Japanese movie).
PlayerUnknown made the Battle Royale mod for Arma 2 (even became PUBG once released as a standalone) by being inspired by the movie.
Obviously, the elements in the Battle Royale is nothing new and has existed for far longer that this manga and its novel, but the novel was the first published work to explains things in a real gruesome and realistic way (at least early in the story). It's also the first to set the rules of Battle Royale (Last Man Standing + Open World + scavenging + part of the world become unavailable over time, shrinking the combat field over time.)
So, yeah, Fortnite is basically based remotely on this or, at least, its novel.