Why did Gu Jiaxing defect from hummingbirds?

In Hummingbird, Gu Jiaxing's mutiny was due to deviance.

After his arrest, Gu Jiaxing was able to endure torture for a time, but in the end he could not escape from the Japanese puppet army and was forced to go further and further. After he defected, he first cheated Lu Yameng's trust as a spy, and after being arrested, he returned to the enemy camp and became the detective captain of the police station, which was very harmful.

On the surface, Gu Jiaxing was bought by the rebel group with Saiteng. In fact, he has defected. He went to the hospital to visit Lu Yameng, who was distressed by Gu Jiaxing and asked about his torture in prison.

Xiuji of the Western Wei Dynasty succeeded Hengshan and was appointed as the head of the gendarmerie. Luo was betrayed as a "hummingbird" by Gu Jiaxing, and Xiwei sent troops to the hospital to arrest people. Luo delayed his escape to save the Japanese girl. Fortunately, he was rescued by the Japanese anti-war alliance and left smoothly after disguise.

Gu Jiaxing ending:

After Gu Jia's mutiny, he first defrauded Lu Yameng of his trust as a spy. After being found out, he returned to the enemy camp and became the detective captain of the police station, which was very harmful. He is a strong tragic figure and an alternative villain image. Rebellion is necessary, and hurting Lu Yameng is even more heartbreaking.

However, after the mutiny, he was cruel and ruthless, and went all the way to darkness, which brought great blows and injuries to Lu Yameng and anti-Japanese organizations. They also became rivals in contests again and again, and were finally killed by Lu Yameng.