What could be the reasons for a genius to lose all his talent in manga?

Perhaps there was a misunderstanding between them. The black cock might have said or done something that his girlfriend misinterpreted, and without proper communication to clear things up, the relationship deteriorated and she left him.

Maybe it was due to a fierce battle. The enemy could have targeted the equipment related to his wings, like shooting down the vehicle or device that supported the wings' function.

One reason could be betrayal by his friends. For example, if someone he considered a close ally made a deal with his enemies behind his back, it would shatter his trust. Another might be lies from the village leaders he respected. If they hid important information or manipulated him for their own gains, Naruto would start to question who he could trust.

Another reason might be related to a plot device in the fanfiction. The author could be using the loss of the mask to create a turning point in the story. It might lead to new relationships being formed or old ones being tested. For instance, his friends might react in different ways when they see his face without the mask, and this could drive the story in different directions.

One possible reason could be the loss of his friends. Naruto deeply values his relationships, and if something were to happen to his friends like Sasuke leaving again or getting seriously injured, it would shatter his happiness. Another reason might be if he fails to protect the village. Naruto has always seen himself as the protector of Konoha, so if he fails in this duty, his sense of purpose and happiness would be lost.

If someone were to insult or harm Hinata, who he loves deeply, Naruto could lose his temper. He's very protective of those close to him, and any threat to Hinata would likely trigger his anger. He has a strong sense of justice and loyalty, so seeing someone he cares about being mistreated would be a big deal.

She could be running too fast, like in a race or just being playful. For example, if she was playing tag with her friends, her shoes might come off as she dashes around.

Maybe he was in a dangerous duel with a powerful dark wizard. The dark wizard could have cast a spell that was specifically designed to maim or disarm in the most literal sense.

Yes, Deku loses One For All at a certain point in the manga.

There could be several reasons. One might be a medical condition like a urinary tract infection which can cause irritation and involuntary bladder contractions. Another could be extreme stress or anxiety that overwhelms the body's normal control mechanisms.