In general, why do many large Eastern European countries break up during the
1980s and 1990s?

Because of the communist block are back then much poorer than the West. People could travel to the West and see the goodness there and live there.

its main object was the establishment of "settlement houses" in poor urban areas, in which volunteer middle-class "settlement workers" would live, hoping to share knowledge and culture with, and alleviate the poverty of, their low-income neighbors.