Selling the ads. Also cooperation with Russian government
He'd have kept VKontakte and never done Telegram then.
"Telegram: Russia lifts ban on private messaging app after it 'agrees to help with extremism investigations'"
https://www.independent.co.uk/tech/telegram-russia-ban-lift-...
And if you believe what Roskomnadzor said:
"The Telegram messenger has deleted over 256,000 prohibited materials since 2021 to date at requests of the Russian Federal Service for Supervision of Communications, Information Technology, and Mass Media, the regulator told TASS."