But this was imprecise and there was a lot of defense systems in place, so still a lot of German capacity survived the battlefield prep.

The Germans had also built cement bunkers for a lot of their weapons that were hard to bomb from the air. They also placed weapons in caves in the cliff side for the same reasons.

The paratroops that dropped at night landed in unguarded fields and then struggled to form up into groups. Attempting something similar under constant fire at the coast would not have worked.

A lot of those paratroop missions were to secure roads and bridges to prevent German reinforcements once the invasion was known.

For most infantry, they needed light to make their way forward at the beach. There were some highly trained Rangers that hit the beach in the dark, like the Rangers that climbed the 100 foot oceanside cliff to storm the guns at Pointe du Hoc.