Why was the redfall trainer retired the game is single player and it can be played offline
Hello! 
There are many reasons why a trainer might be retired. The most common reason is because a trainer is no longer technologically viable due to changes made by the game developers. There are also other reasons such as moral and legal ones (ie, the game developer may have asked us to remove it).
In this particular case, as far as I am aware -
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The game is extremely unstable when used with a trainer (according to multiple cheating communities). It crashes relentlessly, for example.
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The game developers released a 30 gigabyte “update” for the game a while ago, which was actually a complete re-write of the entire game from scratch. Meaning on a coding level it is now a completely different game to the one that the trainer was actually designed for.
WeMod is not the only trainer provider who has retired development of a trainer for this particular game. Unfortunately, it seems that the game developers, whether intentionally or not, seem to have made it impossible for a stable trainer to be made for this game.
One thing you can do is complain to the game developers about this, though there is no guarantee they will grant an audience to cheaters. The reason for the trainer being retired is beyond WeMod/Wand’s control.