From how I understood it, they weren't able to properly block it. Or at least that is the official story. I'm skeptic about this whole ordeal though.

edit: Some article about it says[0]

> Russia on Thursday lifted a ban on the Telegram messaging app that had failed to stop the widely-used programme operating despite being in force for more than two years.

> Some Russian media cast the move as a capitulation, but communications watchdog Roskomnadzor said it had acted because the app’s Russian founder, Pavel Durov, was prepared to cooperate in combating terrorism and extremism on the platform.

dubious

[0] https://www.reuters.com/article/us-russia-telegram-ban-idUSK...