Why the D-Day landings succeeded

Why did the D-Day amphibious landings succeed when many others went badly?

The Allies combined overwhelming firepower with exceptional intelligence, deception, and preparation.

The explanation rests on the extraordinary scale of Allied preparation. Concentrated firepower was supported by extensive intelligence gathering. A large deception and information-warfare effort added to those advantages. The combined effort was intended to make the landing overwhelmingly likely to succeed.