I wouldn't say the "vast majority" of talented bands are in Scandinavia, but they do have a disproportionate amount to the size of their population - like, way more than you'd expect. I have this theory that it's because countries with more socialist economies (like pretty much all of Scandinavia) have a higher standard of living and thus there's moar time for their citizens to focus on the arts. I definitely think I listen to a lot more continental European bands than Anglo-American ones, but with artists like Panopticon, Wolves in the Throne Room, Akercocke, A Forest of Stars, Isis, Mastodon, Weakling, Krallice, and others popping up throughout the last decade, Anglo-American metal is a lot more respectable than it was a decade or so ago.