Maybe he has been unfaithful. In many novels, this is a common reason. If a character cheats on the protagonist, it's clear that he doesn't deserve her love.
She can seek support from her friends and family. They can offer her love, advice and a shoulder to cry on. Their presence can make her feel that she is not alone and give her the strength to move forward. Also, they might share their own experiences which could inspire her to let go and start anew.
One reason could be the purist view. Some fans might be so in love with the original Naruto series that they don't want any fan - made interpretations. They want to preserve the integrity of what Kishimoto created.
Maybe they believe Naruto doesn't deserve fanfic because the creator's vision was so strong. Masashi Kishimoto had a clear plan for Naruto and the world he created. Fanfics could deviate from that original vision. For instance, the complex relationships like Naruto's with Sasuke and Sakura were carefully developed, and fanfics might mess that up.
Perhaps they believe Naruto got too much attention or development in the original series while their favorite side characters were overlooked. So in their fanfic, they express this feeling that Naruto doesn't deserve all the love from fans.
He could be really busy. If he has a lot on his plate, he might not have the time to check out your stories. For example, he could be swamped with work, schoolwork, or other personal matters.
It could be that he's not really interested in that kind of content or doesn't think it's relevant to him. Or perhaps he didn't even notice that you shared the stories.