Because the game's last update pre-dated iOS 11, the game was not available to be played for users at iOS 11 and above, and thus, eventually got a rerelease for iOS 11+ in March 2020 by GameClub, a company that makes old games playable on the current iOS, and thus, the original game was removed from the app store.
What happened to legendary wars?
Legendary Wars was re-released by GameClub on September 3, 2019, allowing the game to be played on an iOS 11 or greater device.