[troad]

This is an important observation, but there were specific technological choices that Old FB made that were conducive to becoming and staying high-trust. For so long as your feed was just your friends and family, you'd effectively perceive FB itself as the place where your friends and family are. It was ingenious.

Facebook figured out how to scale this high-trust environment infinitely (mutual friending required, limiting engagement to friends or mutuals, etc), and then threw it all away when your feed stopped being "your dear friend Jenny got married" and became "your dear friend Dua Lipa wants you to buy her new album".