After winning Zabuza over, Naruto asked curiously,
"Zabuza, what happened in Kirigakure?"
Zabuza had just finished checking his injuries. At Naruto's question, his expression turned serious, and he explained what he knew.
The situation was actually fairly simple. The Fourth Mizukage had suddenly announced to Kirigakure that everything he had done before had been under the influence of Genjutsu, and that he wanted to step down as Mizukage.
After hearing the news, many of Kirigakure's rogue ninja wandering the Land of Water gathered, intending to return to the village and see for themselves.
After all... these rogue ninja were Mist Ninja, too. They had only become rogue ninja because they could not accept the Mizukage's tyranny.
During the Fourth Mizukage's resignation ceremony, Yagura suddenly went berserk and entered Tailed Beast Transformation.
Although his rampage only lasted a little over ten minutes, many people were still killed or injured. Juzo Biwa died trying to save his former comrades by slashing a Tailed Beast Bomb with the Kubikiribōchō.
After that incident, everyone knew the Genjutsu on Yagura had not been completely dispelled, so Kirigakure's leaders temporarily sealed him with Sealing Jutsu.
After hearing what had happened, Naruto could guess what was going on.
It was probably because Minato Namikaze had severely wounded Obito, weakening all the Genjutsu he had placed on Yagura. Every so often, it would stop working or go out of control.
Zetsu must have informed Obito about this, which was why Obito had rushed toward the Land of Water, hoping to reinforce the Genjutsu and bring Yagura back under his control.
There was actually a reason Obito was so obsessed with controlling the Three-Tails and Yagura, using Yagura to strike at all of Kirigakure.
After all... as far as he knew, the Mist Ninja had caused Rin's death.