The reason why Li Chengye lost the crown prince in the TV series " The East Palace " was not explicitly mentioned. Therefore, according to the information provided, I don't know how the Eastern Palace's Li Chengye lost the Crown Prince.

Li Chengye was the character in the TV series " The Eastern Palace ", the second prince. He was a cunning and ambitious man who would do anything to achieve his goals. In the movie, he liked Zhao Sese, but in the novel, he was gay. Li Chengye and Li Yan had a special brotherly relationship, and their relationship was very close. Li Yan was Li Chengye's cousin and beloved general. He was loyal to Li Chengye and was willing to do anything dangerous for him. In the movie, Li Yan was the subordinate of the Second Prince and also the son of the Crown Prince. Together with his father, he supported King Xuande to become the Crown Prince. The old Emperor still wanted to protect Li Chengye even though he knew that Li Chengyin was wronged. Perhaps it was because Li Chengyin was raised by the Empress and the old Emperor thought that Li Chengye was the most suitable heir.
Li Chengye was a character in the Eastern Palace. He was the King of Xuande and had a close brotherly relationship with his son, Li Yan. In the movie, their relationship was described as brotherhood, but some viewers thought that there was a love line between them. In the original novel, Li Chengye's love for men was only briefly mentioned, and there was no specific description. Therefore, according to the information provided, the relationship between Li Chengye and Li Yan was brotherly in the play, but there were also some hints that there might be emotional lines.
Li Chengye was deposed in the 27th episode of the Eastern Palace.
In the drama version of Eastern Palace, Li Chengye and Li Yan showed pure brotherhood. Although there was close interaction and love between the two of them, they did not clearly express their feelings for each other. The original book mentioned that Li Chengye liked men, but there was no specific description. Therefore, the current search results did not provide enough information on whether there was a relationship line between Li Chengye and Li Yan.
The Crown Prince Li Chengji in the Eastern Palace was the Crown Prince of the Feng Dynasty. He had a conflict with the Emperor because he exposed the case of cheating in the imperial examination. The Emperor abolished his position as Crown Prince and ordered him to go to Xizhou to propose marriage for the Feng Dynasty, and then to Xizhou Anhufu. However, on the way to the border, Li Chengji was killed by an assassin sent to assassinate him. Li Chengji's death had attracted the attention of the imperial court. Gao Xian of the Western Region's Protectorate immediately reported the situation to the imperial court and launched an investigation. The characters in the play initially suspected that Li Chengyin was the suspect in the murder of the Crown Prince, but later revealed that it was the Second Prince of the Feng Dynasty who sent people disguised as Danchi people to carry out the assassination. Thus, Li Chengji's death was a major matter for the Feng Dynasty and needed to be handled properly to maintain the court's reputation and deterrence.
Under the ancient feudal system, the eldest son was called the Crown Prince after he succeeded to the throne and lived in the Eastern Palace. Therefore, the Crown Prince was often called the Eastern Palace Crown Prince. In some literary works, there were different images of the Crown Prince of the Eastern Palace. For example, Li Chengyin in the novel " The Eastern Palace " written by Feiwo Sicun was handsome, good at riding and archery, and meticulous in his thoughts. In order to avenge his mother and fight for the throne, he experienced many twists and turns. In terms of feelings, he had a deep side, but also a determination to abandon his feelings for the throne. There were also images of the Eastern Palace Crown Prince in other literary works. Some Crown Princes faced emotional entanglements, such as some Crown Princes not liking the Crown Princess but liking Liang Di. In some stories, the Eastern Palace Crown Prince's marriage was used by the family, and there were complicated situations such as impersonation.
The prince in the Eastern Palace was Li Chengyin. In novels and television dramas, Li Chengyin was the male lead, played by Chen Xingxu. He was the Crown Prince of China and Qu Xiaofeng's true love. The Crown Prince's status was very honorable in ancient times, but it was also full of difficulties and challenges. Li Chengyin experienced the plot of power struggle and rebellion in the play. Therefore, based on the information provided, it could be confirmed that the Crown Prince character in " The Eastern Palace " was Li Chengyin.
In the Eastern Palace TV series, the Second Prince's final outcome was that he was ordered to die by the Emperor. He was executed by the Emperor for framing the people of Danchi, murdering the original Crown Prince, and instigating a rebellion in the palace. As for who the Crown Prince of the Eastern Palace was, the search results did not provide any relevant information, so it was impossible to know.
The Crown Prince of the Eastern Palace was killed by the Second Prince. In order to seize the position of the Crown Prince, the Second Prince Li Chengye killed the Crown Prince and framed the people of Dan Chi. The Second Prince was a person who would do anything for his own ends. Not only did he kill the Crown Prince, but he also wanted to sacrifice the Fifth Prince, Li Chengyin. Therefore, based on the information provided, it could be confirmed that the Crown Prince of the Eastern Palace was killed by the Second Prince.
" Su Jin, Xie Xu, Chu Zhan, Doted on by the Crown Prince of the Eastern Palace " was an ancient romance novel. It mainly described the love and hatred between the main character, Shi Yi, Gu Zhan, and Shi Yuning. The plot of the novel revolved around the resentment of the protagonist after his death in his previous life and the revenge after his rebirth. The male lead was the Crown Prince of the Eastern Palace. After seeing how cute the female lead was when she was young, he brought her back to the Eastern Palace to raise her and doted on her. The female lead eventually became the Crown Princess and enjoyed the male lead's love. This novel received a lot of attention from the readers and was regarded as a work of excellent writing.