The goal is not to affect Kremlin, which they can't in either case, but to use this as a PR opportunity. It is no coincidence that JWTV and their literature is so full of stories of JWs being oppressed in Russia under Soviet rule as this serves several purposes
- Reinforce the basic narrative JWs are oppressed/persecuted by "Satan"
- That worldly political systems cannot be trusted; that current stability/freedom can quickly be taken away
- That events in the first part of the 20th century are connected to today's events, i.e. 1914 is not that far away as this is all one continious unfolding of persecution fitting nicely into their view of world history (this is one more reason why they use older JWs, asides the obvious emotional appeal)
Letter-writing is IMO quite brilliant as it makes it very personal to those who write these letters, the letters can be read on assemblies, and it makes it seem like JWs care more about other JWs than anyone else.