Unexpected religious revival in the post-Soviet space?

Collective prayer of Evangelical Christians in Minsk, 2007. Source: nn.by
In the 1990s, the former Soviet republics found themselves in completely new social realities. Interestingly, despite the decades of atheization, some sort of religious revival took place throughout the whole post-Soviet space.
Millions of Homo Sovieticus type were seeking God. There are different explanations for this phenomenon.