Why are so many of Russia’s vast resources difficult to access?

Vast parts are inaccessible or have harsh winters and/or hot dry summers. It’s costly to access and use the natural resources from the eastern 2/3s of this huge country. While it has rich multiethnic populations, most of the people live in the nearly landlocked, western portion of the country. This vast plain has been the route for numerous invasions from both the east and the west (the last being the Nazis during WW2).