Telegram was going to be banned by Russia unless they handed over decryption keys. We never heard what happened with that, but they’re still in Russia.

Additionally, telegram developed its own encryption method. This is a big no no in the encryption world - it’s safer to use the old method nobody has cracked, than your new method that hasn’t been as tested. There has also been evidence of journalists getting compromised where the information would have leaked through telegram.

Signal is safer