Germany invaded Norway for several reasons.
1. The heavy water plants of Norsk-Hydro they needed for their atomic program.
2. Bases for there Navy, so that it could not be bottled up in the Baltic.
3. It also provided a base for its Air Force.
However it would have been a very poor choice for an Invasion of the Continent by the Allies. You would need to land a force across 500 miles of the North Sea, fight your way across rugged mountains of Central Norway that would have been a defenders paradise, then across Sweden and around the Baltic Sea or another water invasion across the Skagarak to Denmark.
One more point I would like to make is that the Norwegians fought and resisted and many good men died for it. The Swedes did not do a God Da-- thing except use their industry to support the Nazi War Machine. We should have bombed the Swedish Factories as we did the German factories!
"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." -Manuel II Paleologus