It is amazing how much resources Hitler put into the defense of the British owned Channel Islands. He demanded between 10 to 25% of all Atlantic Wall material get dedicated to these Islands.
Lucky for us, Hitler was really dumb and was a terrible commander. He crippled his air force, threw away an army (6th), wasted his Kriegsmarine,he made Normandy an allied victory.
I believe that Germany would have won if they had been a competent military mind as head of state, or even if Hitler just didn’t interfere in military decision.