Might be a stupid question, but why is it always Telegram that gets talked about? Are other secure communications services like Signal, Keybase, etc already blocked?
He is a kind of a rebellious figure in modern Russia, and, as younger generation generally dislikes the regime, he is viewed favorably, and a lot of Russians use Telegram because of that.
So blocking Telegram would be a "we're stronger than you" move by the government.