It was for plausible deniability because of regulatory scrutiny. Regulator's dead now, so now there's no downside and only upsides to spying on your users.
i am guessing that they just dont really need to pretend to care anymore. e2e messaging was a big marketing push, not ever an ideological thing. i assume they no longer believe the marketing benefits outweigh the downsides.
I doubt it, E2E isba huge part of Whatsapp's selling point considering it's exclusively a messaging app. Instagram is primarily a social app with messaging features.
You're thinking of Apple. WhatsApp backups are not stored by Meta. Apple is the company that breaks their "end-to-end" encryption by backing up the encryption keys to their own servers.
Yes. I believe a small percentage of Apple users do this. Unfortunately that doesn't prevent Apple from reading your messages from the backups of the vast majority of people you correspond with.