The Elo rating system was invented by Arpad Elo, a Hungarian-American physics professor, and implemented as a matchmaking approach by the United States Chess Federation in 1960. At a fundamental level, it provides a means to suitably match players in zero sum games by considering their potential ability.

Why is my fortnite lobby all bots?

Without the player level in the equation, Fortnite usually adds bots to lobbies when there arent enough players in the matchmaking pool. Considering the size of Fortnites player base, this is hardly ever an issue unless you tinker with your matchmaking settings.