UAP Crash Retrievals: Why only from 1933 or 1947 onward?

The whole topic of recovering crashed UAP debris leaves me quite puzzled. It seems that military organizations only started collecting these materials in the early 20th century, as if no crashes had ever occurred before then. That seems unlikely. Throughout ancient history—even going back to biblical times—there are countless accounts of unusual objects and phenomena in the skies. Yet, according to modern narratives, these craft only seem to start crashing after modern militaries appear. Ther...