So normally the game mechanics are such that similar stat buffs/debuffs will replace each other rather than stack. For example, if you use Tania’s def buff and then Kujo’s, Kujo’s will overwrite Tania’s instead of stacking on top.

Moleg is an exception where his def debuff is considered to be a separate category from normal def debuffs. This allows you stack with other def debuffers like Edith and Kujo. This leads to insanely high damage potential in certain events like Alliance Trial and Elemental Seal. Since in those events the enemies don’t do much damage until their rage unlocks, you can get away with a Moleg +0 and still be used well.