How did the fourth crusade contribute to the byzantine empire’s downfall? a. it caused the death of the most able and respected byzantine emperor, leo iii. b. it left constantinople permanently damaged after the crusaders looted its valuables. c. it led to large-scale conflicts between the byzantine civilians and military forces. d. it unleashed a terrible plague on constantinople, drastically reducing its population. e. it showed the byzantine subjects the incompetence and cowardice of their rulers.