Perhaps the mask is just a fashion choice or it might be related to a specific story or event in the BT21 storyline that gives a reason for Mang to wear it.
It could be for a more personal reason. Maybe he's going through some internal struggle or self - doubt, and wearing a mask is a way for him to create a new persona, a stronger and more confident version of himself. It's like a shield that allows him to face challenges he might not be able to as the regular Naruto.
Absolutely. Green Goblin always dons a mask in the comics. It not only hides his identity but also contributes to his villainous persona, making him more intimidating and recognizable to readers.
He could wear a mask to protect his loved ones. If there's a new threat in the wizarding world that targets him and those close to him, a mask would be a way to keep his identity hidden so that his enemies can't use his friends and family against him.