I agree. From what I’ve read, it seemed the Allies were not dissimilar to the Germans in their seeming view prior to the British evacuation of Dunkirk: that Allied relative air superiority and naval supremacy would seriously inhibit the transfer of German arms and troops to the mainland. And that perhaps the assumption was that the German maritime capabilities were more limited than they actually were? Unfortunately, it seems the reverse was true…
But then again, some have made the case that the over emphasis on the entire Italian Campaign was itself a major Allied blunder…