Death threats are illegal pretty much everywhere but not necessarily subject to censorship. The threat is the crime, not the content. If someone is already dead, I can safely print a whole hardcover book of death threats against them.
On the other hand, forcibly removing content for the sake of the content is censorship. It can be censorship that most people approve of - which they usually do when the content is sufficiently vile and irredeemable - but it's still censorship.
Correct, the threat is the crime. And German Police was investigating channels that were consistently committing this exact crime on Telegram. Telegram was told these crimes were happening in specific channels and Telegram did nothing. They were now given the choice of no business in germany or removing the channels crime was being committed on.
And yes, content was censored on. But not only death threats were censored but also holocaust denial, eugenics and inciting hatred against ethnic groups (Jewish groups, specifically).
On the other hand, forcibly removing content for the sake of the content is censorship. It can be censorship that most people approve of - which they usually do when the content is sufficiently vile and irredeemable - but it's still censorship.