The emperor seldom loves a person with his heart, so this is worthy of Bai Juyi's admiration. Emperors always protect their own throne, so they seldom really love a person. They are all willing to give up their women for their status. Some concubines in the ancient harem can be said to love the emperor very much and gave their lives to this man, but many emperors regarded them as their own methods. If necessary, they will definitely choose to give up these concubines in the harem. But Tang Xuanzong is different. He really loves Yang Yuhuan. Later, when his country was dying, other courtiers advised him to escape, but his heart was still thinking about Yang Yuhuan and he wanted to take Yang Yuhuan with him, but he couldn't. Later, he didn't take Yang Yuhuan with him. He managed to escape, but his heart was still thinking about Yang Yuhuan, hoping that Yang Yuhuan could come back to him. From here, we can see the love between Yang Yuhuan and Tang Xuanzong, and Tang Xuanzong really loved her!
The poem he was asked to write was about love. So he remembered the love between Emperor Xuanzong of Tang Dynasty and Yang Yuhuan. Their love is really touching, so Bai Juyi chose this theme at that time. He wrote this poem to celebrate their love.
In a word, his original intention is actually to praise their love.