Naruto loses himself after seeing Hinata taken out right before his eyes. His anger  triggers the Nine Tails’ chakra to go out of control.
So that triggered his transformation?
هذا ما أثارَ تحوّله؟
Das war also der Auslöser.
¿Entonces eso provocó que se transformara?
¿Eso provocó que se transformara?
Então isso ativou a transformação?
Это его спровоцировало?