Fortnite itself was originally a base-building PVE zombie game that Epic cranked out a battle royale mode for in a couple of months after seeing that PUBG (which at the time was a janky, unpolished and presumably cheap-to-develop standalone version of an ARMA mod) was a huge success. Then after it's out, Epic restructures behind it as a cash cow, makes it into a modding platform, uses it to improve Unreal Engine, etc.
Minecraft was a little solo project in Java - now 350m copies sold. It didn't start off as a platform for other games, available on every console with cutting edge graphics and $100m in marketing spend behind it.
Ark sold 80 million copies. It was an Early Access game on Steam by a team of 35, then it took off and they ported it to everything.
Battle Royale's been done and been a huge hit for PUBG (2017), then Fortnite, then Warzone. I think it's about time that people would be getting sick of it, same as open world survival crafting games were the big thing (Minecraft, DayZ, Ark) and MMOs. Next Battlefield is $400m, all those other big hits were probably more in the $100k-$1m range. Maybe it would be better to make a bunch of $1m-$10m range games, see which one is a hit, then move resources behind it. I imagine changing the structure of a big business like EA to be able to make a move like that would be a very, very difficult undertaking though.