Apple Invites

Brilliant move.

The transition of the major social networks over the last 10-15 years -- from being a space for friends to interact to being a space to consume content produced by "unconnected" entities like influencers -- has created a huge opening for someone to claim the friends and family network. There is no one better positioned (at least in the U.S. where iPhones are the majority handset) than Apple.

I think Apple already has claimed the "friends and family network" via iMessage. Did Facebook go to a groups/influencer algorithm by choice or is it the result of IRL friend posters all moving to private chats once everyone got iPhones?

That's only true if everyone in the group has an Apple phone, which has decreasing probability with every additional member. Excluding people from a conversation because they don't have the right brand of phone would be pretty antisocial.