It usually wasn’t conversations that were at issue. People would engage in criminals acts, such as trading child sexual abuse media in large unencrypted group chats. Law enforcement would find links to those chats, join them, and observe criminal acts, leading to court orders to Telegram to disclose whatever identifying information it had about the offenders, such as phone numbers and IP addresses.

Telegram intentionally split storage of that kind of information across jurisdictions that do not cooperate so that it was effectively impossible to obtain orders for all of them. They bragged their marketing materials that they have never complied with a court order for user information. Taken as a whole, I see that as intentionally facilitating child abuse.

Signal’s approach is pretty much the inverse; rather than hoard data about users and shield people they know have done evil, Signal has ensured that it does not know the contents of any conversation, nor anything about users other than when they created the account and most recently accessed it.