Elden Ring: Nightreign is also a co-op PvE game that has anti-cheating in it. The most common way people cheat is by fudging then items equipped to their character that slightly alter their stats and abilities. Since the game is rouge-like and all of your character information and equipment you can assign before entering the game is handled locally then all it takes is editing your save file which the game and server have no way of (or makes no effort to) detect.

Also, after a brief period, all of the cheaters disappeared because just repeatedly winning a PvE game get boring.