The main elements of the shift are that the Democratic Party built, under FDR, a coalition that could and does viably win national and state and local elections while before him, it could only do so in cases like Grover Cleveland and Wilson where the Republicans were infighting to a point a Dem could sneak in through the back door. Both parties had liberal and conservative wings. The Taft Republicans were the prototype of today's conservative Republicans, Roosevelt's wing fell apart by the Reagan era and has been dead for a long time as of the 2000 election.

The Democratic Party went from a sectional and state party that occasionally won national elections to a national party based on a coalition of marginalized groups and Black people starting to switch from GOP to Dem under the Coolidge Administration and Harding Administration. The biggest cause of the switch was Republicans having a majority in Congress and refusing to address lynching, at the time.

It's more of a set of assumptions about 'Old Europe', of which the Basques and the Sami are the last remaining traces, versus the Indo-European versions. The various Indo-European cultures that were ancestral to modern cultures wrote about these cultures around them or they left linguistic traces in substrates and perhaps in the ways that Indo-European languages evolved and why they evolved in those ways.

It's also the same thing as why Arabs are Indigenous to the Middle East after conquering it in the 600s but the Greeks they replaced weren't in spite of being there for 1,000 years prior to that. The concept does have some semantic wordplay and double standards attached IRL.

It's not really that odd, it's a reality that Indo-European peoples moved into Europe like they did into Iran and the Middle East and India. There were peoples already living there, of whom the Sami and the Basques are the sole cultures to make it, and the Magyars and Finns are peoples who moved after the Indo-Europeans arrived in much more recent times.

They're descendants of cultures that migrated in a long time ago, though this applies to plenty of cultures throughout history that never get all the caveats applied to them.

Karelians are a Finnic people and Finno-Ugric peoples 'originated' in the interior of modern Russia. Finns and Karelians and Hungarians are all distant kin, linguistically (the Hungarians) or the equivalents of Germans and Austrians (Finns and Karelians). The other indigenous group are the Basques, not the Karelians.