The reason why LJ is so popular is Russia is historical. 1) It was one of the first blog platforms used there . 2) It was US-based and hence provided a comparative freedom of speech (somewhat very actual in the post-soviet Russia with its 282 article of the criminal codex; you could not imagine what happened here in the mid 2000-th - even revolution/riots were conspired there, there were posts exceeding 10 000 comments - the limit of LJ :) ). 2) Finally it has some unique features like LJ communities, threading comments - somewhat unavailable with many other services and social networks. After reaching its popularity in 2000-th and accumulating the top Russian bloggers, the new ones will always stuck to it...