WhatsApp supposedly uses Signal protocol.

Why is THAT not blocked? Certainly they wouldnt roll their own encryption and bypass Signal security protocols after having Moxie come in, right? Right????

Telegram is not secure, I guess if you can listen to it better not block it.

I mean it was blocked before Signal was blocked. Russia somewhat famously badly broke their Internet trying to shutdown telegram... and eventually gave up.

I'm guessing Signal finally has enough market share to get the Russian government's attention but not enough market share that they think the web of proxies that kept Telegram online will keep Signal online.

On April 16, 2018, the Russian government began blocking access to Telegram, an instant messaging service. The blocking led to interruptions in the operation of many third-party services, but practically did not affect the availability of Telegram in Russia. It was officially unblocked on June 19, 2020

Some say it was unblocked because they made a deal with Durov. Another opinion is that too many people and services including officials continued to rely on it even during the time it was blocked. Regardless, Telegram did a huge job on circumventing those blocks.

It isn't private