I think this part is why:
"The graduate program in history is small, highly selective, and especially well supported by the University. If a student is admitted, the University will provide a competitive financial package that will include a stipend for living expenses, remission of tuition, and cover fees and health insurance."
More attention and funding means fewer students. Plus if you look at last years results for UVA the number of acceptances seemed extremely high for a top school.