Facebook has many illicit groups and Mark Zuckerberg was never charged with anything. I assume this is more related to privacy where US government has backdoor to Facebook while doesn't have one to Telegram.
Maybe because their legal compliance strategy is something other than "we will only, and only possibly, comply with law enforcement requests if it concerns terrorism"?
To quote Telegram's from https://telegram.org/privacy:
> If Telegram receives a court order that confirms you're a terror suspect, we may disclose your IP address and phone number to the relevant authorities. So far, this has never happened. When it does, we will include it in a semiannual transparency report published at: https://t.me/transparency.
So yeah, Meta takes it really seriously. It doesn’t work perfectly because the scale is mind-boggling, but it’s probably the best system of this kind at this scale, and it is constantly being evaluated, red teamed, and improved.
Source: I used to work on FB Groups.