Lack of strategic importance: Norway was not considered to be as strategically significant to Russia as other areas of Europe, such as the Balkans or the Baltic States. Russia's primary goal in World War II was to secure its western border and establish a sphere of influence in Eastern Europe, and Norway was not seen as essential to these objectives.
Geography and climate: Norway is a rugged, mountainous country with a harsh climate, which would have made an invasion and occupation extremely challenging for Russian forces. The country's long coastline and numerous fjords would have made it difficult to establish control over the entire country, and the weather conditions would have hampered military operations during much of the year.
Norwegian resistance: Norway had a strong and well-organized resistance movement, which was formed shortly after the German invasion in April 1940. The resistance movement was able to effectively disrupt German supply lines and communication, and it also provided valuable intelligence to the Allied forces. This resistance would have made it even more difficult for Russia to occupy and control Norway.
Allied intervention: The United States and Great Britain were both interested in preventing Norway from falling under Russian control, and they provided significant support to the Norwegian resistance movement. In 1944, the Allies launched Operation Overlord, a large-scale invasion of Normandy, which effectively diverted German resources away from Norway and helped to secure the country for the Western Allies.
In summary, Russia did not occupy Norway due to a combination of factors, including the country's strategic insignificance, the challenging terrain and climate, the strong Norwegian resistance, and the intervention of the Allied forces.