As the CEO he should be responsible for anything he was facilitating as part of his business, and that would include crimes committed using telegram that he was aware of and both did nothing to remove from his service and made it harder for law enforcement to prosecute. You know, like how a warehouse owner who knowingly sells space to pedos and does what he can to keep the police from searching the warehouee is complicit.

There are some circumstances where they are unaware or only take halfhearted measures, but in this case it looks like he is being investigated for actively working to enable criminals, including pedos. As the head executive, he doesn’t have to do it personally if he is directing staff to make it happen.

Edit: explaining the logic behind something isn’t the same as agreeing with that logic

Isn’t the main problem that most people don’t use the E2E encrypted chat feature on Telegram, so most of what’s going on is not actually private and Telegram does have the ability to moderate but refuses to (and also refuses to cooperate)?

Something like Signal gets around this by not having the technical ability to moderate (or any substantial data to hand over).