Speculative. We don't know why he is in jail. Maybe his lawyers know why, maybe not. Maybe the prosecutor knows, maybe not. We don't know if there's a case. There's hardly anything we do know.
My take is he doesn't reply to LE requests related to CSAM. That is one of the few things we (as in: our governments) don't like anywhere in the world, and Telegram is known to respond slowly to [such] requests. But I won't pretend I know for sure. Cause either way, it is a neat honeypot compared to technically better protocols.
Telegram is structured like a mix of a social network and a blogging platform. You find people you trust and read them. Sometimes they would repost someone else and if you like what they write you can read them too.
https://www.ft.com/content/c5d40e3c-9f9c-43dc-a467-1c713b40c...
That makes me wonder if Telegram was always a Russian spook op and its [ineffective] banning just a ruse.
I don't think any of the major platforms are independent of some spook oversight.
With Telegram, as you say, the Russian ban (somewhere around 2014) could have been designed to signal that Telegram is not run by the FSB.
This arrest, on the other hand, could have been intended signal that Telegram is not run by the CIA.
There have been a couple of house searches, extradition orders and YouTube bans all in the last two weeks for pro Russian commentators. I always wonder if these individuals are genuine or actually working for the U.S. gov.
Anyway, together with the latest crackdown of the EU on Musk all these events could be genuine and not staged.
after watching Carlson's interview with Durov have come to think he may be the genuine article. Very interesting bit his relating us agents trying to recruit a dev and pushing some specified but alas unnamed oss libraries to use in Telegram.