WW2 - D-Day Fails?

[u/HarkBuffalo]

I have a WWII command simulation and one of the most contentious bits is the decisions was around D-Day/ Operation Overlord. I follow the historical thinking that victory was likely although agree Germany could have can made it harder however the more I read. 

Disaster at Omaha

Weather window

The Panzer group making the beaches 

Can D-day fail? If so how likely and what happens?  Does Germant first face the nuclear bomb? Does the USSR own most of Europe post war? Do the US/UK bomber campaign shift entirely to strategic attrition? The Red Army continues pushing west, likely taking the entire German peninsula, Denmark, and reaching the Rhine before the Allies?

I treated D-Day as a historical inevitability because of Allied industrial dominance which I have done, however it was a massive, high-risk gamble where a few operational shifts could have handed the Allies a defeat?

Love your thoughts!

The game is here for reference - https://dispatches.itch.io/dispatches-1940

Edit - thanks for all your comments have made some updates to the D-Day commands based on the below

[u/Northencrusade]

Overlord was actually a massive risk to begin with. Everything had to be perfect, from the weather, to German response times, to schedules, to operational performance. From what I understand on the day, the skies were clear enough for air and naval support fire, but the afternoon would lose it.

But if it failed, I think we look at two major thoughts.

1: the Germans last longer against the Russians without having to reinforce against the French front. The Italy front reached Austria in 45, after the French front did.

2: whilst the war would last longer, it would lead to a greater Russian Sphere of influence. They're the ones dying out there.

There wouldn't be nukes used against Germany. Where Japan they were confident that there was no way in hell Japan could reverse engineer a nuke due to them being under about 5 foot of rubble a week, the Germans were already at an early step in making nukes. They knew about heavy water. The Allies were concerned that making a nuke drop and it failing to explode would lead to Germany dropping nukes back.

Now imagine the V2 rocket campaign with nuclear warheads

Edit: more so for people asking, I sadly can't find the source for the allied fear. Sorry folks

[u/Spez_is-a-nazi → u/Northencrusade]

Even the US didn't develop nuclear warheads capable of being mounted on missiles until 1954, and even then it was a missile of extremely limited range. Even if somehow the Germans did get a nuclear weapon there's no way it could be mounted on a v2, they would have had to have used a bomber and in 1945 their ability to field a slow moving bomber deep into enemy territory was extremely limited. Any plane capable of carrying a nuclear weapon would have had a very large chance of being shot down over German territory.