Between not participating in colonialism (which Western Europe got a huge boost from it and the related looting), being conquered and kept as tax source by the Ottomans, bloody post-liberation territorial disputes wars (because of their soft borders), getting fucked over by western powers in WW1 and WW2, getting caught up in the Eastern Bloc and staying underdeveloped, the plundering of their national resources by local rising business moguls, foreign "investors" in cahoot with the former, mafias, EU policies benefitting the center against the periphery, post-1991 demographic collapse going on, both from declining birth rates, but also because millions of people immigrating
...it's amazing that they still ended up as decent as they are today in the first place...