In summary, just like the Germanic languages of English and Frisian resemble each other in many respects, they developed parallel from a root source and may have had limited exchange through their existence. In the case of these games, the Germanic Pagan cultures are the root source, so there will obviously be some similarities and perceived influences despite being different.
Oh, and of note Tolkien's Middle Earth was also supposed to be pre-historic earth. I think a major difference between why Tolkien is seen as high fantasy and Conan as low fantasy is because in Tolkien the reader is relatively omnipotent (especially with the Simarillion [spell?]) whereas in Conan you see the world more on the ground level and through Conan's eyes for the most part. Personally I would qualify Tolkien as low fantasy, but that's me.