Privacy laws (2020), which aim to reassert people’s control over their private correspondence.
Moderation had continued under the terms of an exemption, which expired. Chat Control 2.0 would have mooted it; CC2 didn’t pass (nice job all!); so they’re maneuvering to extend the status quo.
To the “impossible,” though: I vaguely remember, many years ago, reading through pretty cool research about content-agnostic approaches to moderation at scale. Many of which, IIRC, informed WhatsApp’s approach. They seemed to focus on damping the social dynamics of content that ended up being inflammatory, malicious, or extractive.
Things like restricting the number of times any specific message could be forwarded, or constraining the size of audience that somebody could address with malicious messages, or network analysis overlaid on messages that recipients voluntarily flagged for review. (And in WhatsApp’s case, segregating explicitly commercial speech in “business accounts” outside the e2e veil.)
I’m sure this is an entire field of study that I’m doing no justice, but I’d welcome any entry points to the current literature!