Spoiler The Boss Remains (Majora's Mask) are akin to Transformation Masks, and thus the Fierce Deity's Mask was supposed to turn Link evil.

[Hyrulian Hero]

Quick thoughts. If the Boss Remains are transformation masks, why don't the moon children transform when they wear them? The same with Majora's Mask, the Skull Kid doesn't turn into Majora's Wrath, the mask sheds him. Transformation masks also don't necessarily control the wearer by their nature. Link takes on the form of the dead when he wears them but they don't control him.

 

[Uwu_Oocoo2]

Quick thoughts. If the Boss Remains are transformation masks, why don't the moon children transform when they wear them? The same with Majora's Mask, the Skull Kid doesn't turn into Majora's Wrath, the mask sheds him. Transformation masks also don't necessarily control the wearer by their nature. Link takes on the form of the dead when he wears them but they don't control him.

With the way the inside of the moon is, I wouldn't be surprised if they aren't really wearing the masks and are simply wearing a representation of them. It strikes me as the type of area where everything would be an illusion. Additionally, transformation masks made from the dead may be different from the ones used by Majora since he is an evil entity presumably using dark magic. (This is all speculation so uh take it with a grain of salt but that's what would make sense to me)

 

[Guinea]

My headcanon is that the Moon Children are the dark tribe the Happy Mask Salesman mentioned, and that the Happy Mask Salesman is actually Majora, since he referes to the mask as his.