Because the music Rong Qi played had a melody almost identical to the one Rong Feiyu played on the piano earlier. But there were differences as well. Rong Feiyu's piano piece had a lighter and more sorrowful rhythm, while Rong Qi's violin piece seemed grander, with an ethereal melody that conveyed not sorrow but disappointment and melancholy.
Listening to Rong Feiyu's piano piece evoked the image of a couple in love suddenly breaking up, but Rong Qi's violin piece seemed to transport people back to ancient times, when a warrior who had fought battles in his youth but remained unfulfilled in old age, filled with regret and melancholy. The latter piece was more emotionally evocative.
Or one could say that the latter piece was of a higher level compared to Rong Feiyu.
Everyone felt that the same melody played by Rong Qi was truly brought to life in her hands.
A true master should be Rong Qi playing the violin.