The truth is that every soviet country was already in deep economic trouble, that's what caused the collapse. There was also a ton of corruption before the fall of the USSR. The only difference was that during the cold war, the USSR wanted to pretend that their way of life was as good or better than the capitalist west. That meant that there was a ton of propaganda making things seem better than they were, and a ton of censorship about how it was in the west. It meant that the corruption was kept relatively quiet so that it didn't embarrass the government so that it looked weak compared to the west.

As soon as the USSR collapsed, they stopped putting all the effort in to censor the west and make the USSR seem great through propaganda. That resulted in people thinking that the economy had collapsed after the USSR, when the truth is that the actual economy was simply finally revealed to them.

how the German reunification worked out. It was quite a mess that they plowed through.

Well, I'm not sure if you can really say that reunification was ever properly completed.