When I think of "D-Day" I have questions.

What was the military necessity? Same for the Pacific island campaign. If your opponent's airforce/navy has been decimated, his allies surrendered, most of his army trapped/captured in Russia, is he a threat? Isn't surrender or collapse imminent? If so, what is the hurry? Why sacrifice/commit ground troops? Especially if only the enemy is marooned on useless islands? What harm would occur if they were left there until they died naturally or surrendered or committed suicide? Won't some who want to live/go home rebel causing the others to do the same and resulting in no need to lose a single life by forcing the immediate confrontation? If some action is needed, some direct confrontation, won't bombs or shelling from the sea be the best option? When military leaders used to lead or at least be in the thick of battle, was more thought put into strategy? When the generals/politicians have no chance of dying, are they as careful?