What is the reason why the guests in "Red Cliff Fu" "entrust their wishes to the platform of hatred", and express the author's perception of life?

The guests thought that even a hero like Cao Mengde, who was famous at that time, was just passing away. Moreover, the right-hand man of Yuqiao Zhu Jiang's life was as short as a fly, as small as a drop in the ocean, and his dream of becoming an immortal was out of reach. He couldn't help feeling sad and expressed his sadness through the flute. "