In addition to what others are saying… I don’t recall the number but somewhere between like 1.5 and 3 million residents of the former GDR moved west after reunification (and that’s on a fairly smallish population base). That’s because the west completed nuked the east’s economy and industrial base, honestly not that far off from what Russia experienced in the 90s (common for West German companies to buy a factory in the east for pennies and then close it down to avoid competition). But the difference is Russians had nowhere to go but East Germans could head to the west.

So in those conditions - not unlike what you see in the Rust Belt or small towns in the US - the only people who remain are those who can’t or don’t have the employable skills. And they’re left to languish in economic misery. Stew in that for a few decades and you’ll probably be pretty receptive to anyone who comes by to say your problems are all due to some “other”.