In this fanfiction, Naruto might be pushed to attack the Five Kage Summit due to some misinformation or a threat he perceives to Konoha. Maybe he thinks the Kages are planning something against his village.
In such a fanfiction, there are many possibilities. Naruto could have been framed for a crime he didn't commit that made the Kages see him as a threat. His attack on the summit could then be an attempt to clear his name or expose the real culprit. Also, it might be related to some hidden power that is manipulating him or the political situation in the ninja world has become so complex that he feels the need to take drastic action at the summit.