Norway's strategic imporance well stated here

Battle of the Atlantic - The Allied loss of Norway brought German warships and U-boats many hundreds of miles closer to the Atlantic convoy routes and in time within close range of the Russian convoys that followed the June 1941 German invasion. Britain's blockade line from the Orkneys to southern Norway was simply outflanked. Within a matter of days the first U-boats were sailing from the Norwegian port of Bergen.


The writers who debunk the value of Germany's move on Norway would have difficulty arguing against this. Ship sailing to France needed Norway as sailing through the channel was much more dangerous.