Being intrigued by the first fight between Goku and Jiren, Vegeta jumps in to battle Jiren to test his strength and potential. Vegeta’s goal is to not only beat Jiren but to also unlock Ultra Instinct.
To mimic Goku’s limit breaker moment, Vegeta tries to let his body control his movements and not his mind. The battle is hard fought and intense as Vegeta pushes back Jiren. What decided round 1 of the fight between Vegeta and Jiren was his arrogance.