Kind of ironic that he left Russia only to end up being arrested in the west for building a platform that the ruling class here can't control.

He really doesn’t need to install backdoors. In Germany we know since 2018 that the BKA (German federal criminal police office) can access Telegram accounts and everything they write easily just because most content in Telegram is not encrypted by default until today.

There was actually a german court case where the BKA told how they easily access Telegram accounts with a warrant without support from Telegram. And to be honest, if the BKA can access them, other three letter agencies will be able for sure. German agencies are not known for their technical skills.

I mean they could also arrest Marlinspike (Signal founder) or Acton if it was just for building a secure platform, since Signal is way more secure than Telegram but they walk free across the world.

Also why they don’t arrest Zuckerberg (or Marlinspike or Acton): Facebook at least tries to delete child porn and drug trade from their platform while Telegram seems to endorse this kind of content as long as it pushes their platform.

I don’t understand what he did wrong.

Created social media platform which went very popular but isn't controlled by US media oligopoly or their subsidiaries.