My theories in order of my opinion of likelihood:
1. Nick just didn't fit in. If you follow any of the Penn State guys on social media, they seem to be a really tight knit group. Bo, Nolf, Cenzo, and Zain seem like they are all best friends. Cutch is in that group as well as is Hall to a lesser degree. They all seem to have a goofy disposition and don't really take much too seriously. Nick's demeanor always seemed to be very serious and focused. I feel he may have felt like an outsider surrounded by guys that he didn't fit in with.
2. Suriano's father is pissed he didn't redshirt this season. He got hurt and didn't have a shot at 4 titles.
3. They weren't satisfied with his training partners. Hear me out here. Who was Nick's #1 partner this season in the room? Cortez. He got hurt a quarter of the way through the season. So Nick was drilling with guys who weren't anywhere near his level. Now Cortez is going up to 141.
4. Nick wants to move up to 133 but Cael is blocking it due to the Keener transfer. A grad transfer just transferred in to fill a gap and if Nick wants to move up, Keener would be benched and they wouldn't have a suitable 125.