One of the largest contributing factors to Fortnite taking forth place is that the game isn't available on the Google Play Store, making it significantly less accessible for Android users.
In a dataset only looking at games downloaded from the Apple App Store, Fortnite is at the very top of the list.
Tim Sweeney, the founder and CEO of Fortnite creator Epic Games told Business Insider that they decided not to host the game on the Google Play Store in order to avoid paying a portion of their profits to Google.