Why do more Russian aircraft crash in this region than any other?
For the same reason that more Renaults break down than Ferraris, that there are more of them. I suspect that if you converted the raw figues into percentages the picture would look different.
The aircraft in that region are badly maintained and badly piloted in many cases. It's more of a reflection on the operators that they crash frequently than on the manufacturer. The same applies in Iran where they have had a number of TU-154 crashes.