This might be a plot in many time-travel novels because modern technology had been quite advanced after World War II. Many time-travelers might find it difficult to survive in modern society. Therefore, many time-travel novels often delayed the historical process until after World War II to give the protagonist enough time to adapt to modern society. Other novels might also take into account the impact of World War II on human society, especially the destruction and casualties caused by the war. In the novel, the protagonist might travel back to World War II to help change the course of history and reduce the damage and casualties caused by the war. This was also a plot design. There were many plots in time-travel novels, some of which might have taken into account the influence of modern technology and historical processes, while others might have delayed the time until after World War II.