77 pages of messages sounds like it's only a small percentage of communication in that group. I can imagine (also based on other comments about organizations like this being infiltrated by law enforcement) their communication networks are a lot more involved than Telegram chats or other "honeypotable" systems. Snowden revealed (or confirmed our suspicions that) the NSA has backdoor access to all major American based social media / communications, and the media broke at least twice about a major 'encrypted' chat / secure phone provider being compromised causing hundreds if not thousands of arrests worldwide.

(note: arrests, because whether the chats were recorded legally and are admissable to court is a whole different matter)