1. Xiong is the grandson of a disciple abandoned by the Yang family, and Emperor Wen of Sui is the 89th head of the Yang family. This family background may make the bear feel nervous and afraid in the face of Yang Shi, which stems from the depression in his blood.
2. As the captain of the bear, Yang Jian has strict requirements for the bear. This may make the bear feel stressed and scared when facing Yang Jian.
However, please note that these are all speculations based on information and may be biased from the original work. I suggest you read the original work to get more accurate information.