The reason why Cao Zhi wrote "seven-step poem"

Cao Zhi was the third son of Cao Cao and later usurped the throne as emperor. Because Cao Pi was worried that leaving Cao Zhi and Cao Xiong (the fourth son) would have future troubles, he put pressure on them on the grounds that his father did not visit him when he died. Cao Xiong committed suicide because of fear. But Cao Zhi was brought into the imperial court. Finally, Bian Shi, the mother of four brothers Xelloss, began to plead, and Xelloss reluctantly gave Cao Azhi a chance to blurt out a poem within seven steps, otherwise he would be killed without forgiveness. Cao Zhi wrote this seven-step poem. Cao Pi understood the truth in Cao Zhi's poems: if he killed Cao Zhi, he would be laughed at by the world, but his greed still made him lose his mind, so he put Cao Zhi under house arrest. Finally, Cao Zhi died of depression under his brother's house arrest. At the age of 40.