Well that too, but Riddler did take Stalin's idea of putting people in the Gulag, just like Stalin took Riddler's idea of killing others that could be a threat to his position.
Because Riddler took that idea, hence the holocaust.
There's a number of reasons Stalin was a total jackass that ruled the country with a massive iron mustache, but I've also heard the people miss his doing everything for everyone and tightening down. I suppose things weren't TOO bad as long as you weren't a peasant farmer, or as long as you never made a mistake.