Telegram, including secret chats, is not blocked because Russian elites happen to use that, too.
I could put on my tinfoil hat and say if signal is blocked but telegram isn’t, maybe that means that telegram isn’t as secret as they make it out to be.
No need, all you have to do is read the whitepaper. they home brewed the encryption algorithm and nobody actually knows if it’s worth a damn. That’s not exactly a secret.
They don’t have reproducible builds afaik (unlike Signal). You can have a completely different code running on your phone than on GitHub.
Besides, who is using Secret Chat anyways? All default chats and group chats are unencrypted.
Telegram is shady as fuck and also afaik only uses end to end encryption in „secret“ one on one chats.