The narrator bought the desk which was in bad condition because he wanted a desk like it and he was not able purchase a desk because it was so costly. That is why he bought the desk

In the story "The Best Christmas Present in the World" by Michael Morpurgo, the narrator buys the desk in bad condition for several reasons.

Curiosity and Intrigue
The narrator was intrigued by the desk's unique history and connection to a soldier from World War I. The discovery of the letter inside the desk piqued his curiosity and motivated him to learn more about the soldier and his story.

Sense of Connection
The desk symbolized a connection to the past and to a significant historical event. By purchasing the desk, the narrator felt a sense of responsibility to uncover the soldier's story and ensure that his sacrifice was not forgotten.

Desire for Redemption
The narrator may have felt a sense of guilt or remorse for initially overlooking the desk due to its poor condition. By buying the desk and delving into its history, he sought to redeem himself and make amends for his initial indifference.

Appreciation for History
The narrator had a deep appreciation for history and the significance of preserving artifacts that tell a story. By acquiring the desk, he was able to contribute to the preservation of the soldier's memory and honor his legacy.
In conclusion, the narrator's decision to buy the desk in bad condition was driven by his curiosity, sense of connection to the past, desire for redemption, and appreciation for history. This act of purchasing the desk ultimately led to the discovery of a poignant and meaningful story that had a profound impact on the narrator.