The correct answer to this open question is the following.
The discovery in the Dunhuang cave helped historians in the following way.
Historians benefited so much of the discovery in that it gave them the chance to study and interpret the documents found in the archive; more than 50,000 documents, textiles, paintings and artifacts of that time that help them to explain the society at that time. The discovery helped historians to understand life and society of that time, to understand folk literature about ordinary people, that helped change the perspectuve historians had with respect of farmers and the government. These ideas help historians to have a better understanding of life and people relationships in those years.
We are talking about Qianfodong, the "Caves of the thousands Buddhas." This magnificent place is located in Dunhuang, a busy place for traders during the Silk Road years, in Northwest China.